LED railway signal detection rather than recognition is affected by both refractive and non-refractive blur

LED railway signal detection rather than recognition is affected by both refractive and non-refractive blur | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article LED railway signal detection rather than recognition is affected by both refractive and non-refractive blur Timothy Nguyen, Jack Choy, Mei Ying Boon, Vanessa J. Honson, Stephen J. Dain This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8052714/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 9 You are reading this latest preprint version Abstract Purpose: Previous research has reported a significant effect of refractive defocus on correct identification of red signals. The purpose of this study is to investigate the effects of both refractive defocus and non-refractive defocus (using Bangerter filters) on the perception of rail signals using the Railway LED Lantern Test (RLLT). The RLLT is the simulated practical test nominated in the Australian National Standard for Health Assessment of Railway Safety Workers. Method: Participants were 19-59 years old, best corrected visual acuity (BVCA) was required to be no worse than 6/9 binocularly. Subjects with current or active ocular conditions were excluded and sufficiency in English was required. Best corrected refraction, visual acuity and colour vision was assessed. Participants carried out the RLLT binocularly under five conditions: best corrected, +0.50DS, +0.75DS and Bangerter filters 1.0 and 0.8 Results: 10 male and 10 female subjects completed the study; age range 20 to 25 and mean age 22.4 ± 1.1 years. BVCA was 6/6 (logMAR 0.0 or better. Errors occurred far more often with red than yellow or green ( p <0.0001) and with Bangerter filter blur more than refractive blur ( p <0.0001). Failing to see a red signal rather, than misnaming the red as yellow or green, was the predominant error (p <0.0001) and induced far more frequently by Bangerter filters than refractive blur ( p <0.0001). This error was far more common than miscalling red as yellow (p <0.0001). (Paired t-tests) Conclusion: These findings suggest that a large proportion of errors are due to not seeing the red signal rather than miscalling the red as yellow or green. Non-refractive blur was found to cause a greater increase in colour errors. colour vision railway signals occupational safety vision standards blur Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Introduction Signals passed at danger (SPAD) are events where a train passes a stop signal without authority. [1, 2] Previous research has reported refractive defocus as being a significant factor in signal recognition that can occur when looking through low added power lenses, such as the corridor of progressive addition lenses (PALs). [3, 4] A survey of Australian and New Zealand rail organisations found that SPADs occur up to 62 times annually resulting in associated delays averaging 270 minutes costing $ 153,000 and are accompanied by preventative and reactive costs of up to $ 520,060 and $ 1.87 million annually respectively. [5] A previous study in the 1980s reported no significant situational or personal factors underlying 224 SPADs events in the Netherlands. [6] Weather and adverse conditions such as darkness, rain and fog did not contribute to SPADs. These events were however more frequent in the morning, particularly 4–9 am, and at the start of locomotive drivers’ duty periods. The authors alluded to fatigue as possibly being the major factor. Drivers committing SPADs also had lower reaction scores on a multi-choice reaction test and less occupational satisfaction. The effects of optical defocus on rail signals misperception were studied after a report of red signals appearing orange-yellow when viewed at long distances through progressive additional lenses (PALs). Studies by Wood et al. [3, 4] found a significant percentage of red signals reported as appearing orange-yellow in the presence of a bright background or glare source and at longer distances through spherical refractive blur in both field and laboratory environments. The follow-up study [4] involved a change in protocol testing using signals satisfying the Australian Rail Track Corporation (ARTC) Engineering standard Light Signals SPS 11 [7] (now superseded by ARTC ESA-04-01 Colourlight signals and indicators [8]) where results were similar. The authors did not use the conventional names of signalling practices as the set responses were a forced-choice of “red” or “orange-yellow”. This is not reflective of signalling practices and does not reflect decisions that rail drivers need to make. They did, however, consider their observations to be relevant to the occurrence of SPADs. Holmes [9] observed that “For example, an observer presented with a bluish-green light and asked to call it 'green' or 'not green' would almost certainly call it 'not green' but if asked to call it 'green’ or 'red', he would call it 'green'. The limits of the area on the chromaticity diagram called 'green' when the choice is 'green' or ‘not green' would be different from those when the choice is 'green' or 'red'. Further, the choice made by the observer will differ according to whether he knows the colour of the light to be one of two or three alternatives, or to whether he is told that the colour may be anything, because in the first problem his decision may be reached by rejecting the alternatives whereas the second problem requires positive recognition of the colour.” As a consequence, the current research has not reflected modern Australian signalling practices (which are mostly LED) or the prevailing colour naming (red, yellow and green) into their methodology so the practical significance of the observations is unclear. Topley [10] and Cole & Vingrys [11] report visual acuity effects on performance of the Board of Trade (BoT) Lantern and Holmes-Wright Type B (HWB) lantern, respectively, but the types of misnamings made are not reported. Only one of their 100 subjects had a visual acuity of 6/9. Cole & Vingrys report that the BoT Lantern is a stringent test like the HWB lantern. Since it was designed for maritime use, the HWB uses a colour code of red, green and white and required sighting distances are mainly 6 nautical miles (11.1 km) for white lights and 3 nautical miles (5.6 km) for coloured lights. [12] Railways use red, yellow and green for fixed signals and the critical distance is 1.6 km when locomotive driving. [13] The railways do use red, green and white for their hand-held lanterns. Cole & Vingrys [14] reported that the HWB lantern is more stringent than the Farnsworth Lantern (FALANT),which was also originally developed for naval use and also has a red, green and white code. [15] The FALANT and Railways LED Lantern Test (RLLT) are essentially equivalent in difficulty. [13] The current study aims to investigate the effects of both refractive and non-refractive defocus on the detection AND recognition of LED rail signals. This current study uses colours and colour names (red, yellow and green) as used in trackside signalling and using the official colour vision test of the Australian railways. The RLLT [13, 16, 17] is a simulated practical test nominated in the Australian National Railway Medical Standards (current version [18]) carried out at a test distance of 6m for those needing to meet normal colour vision standards such as locomotive drivers and at 3m for those needing to detect and recognise coloured signal lights at shorter distances (e.g. station assistants and trackside workers). It is consistent with modern railway signalling practices including the use of the LEDs that are used in signal construction and a range of luminous intensities representative of railway signals in practice. It is possible that the RLLT could be used to identify those at risk of mis-naming red under conditions of defocus. Using the RLLT should be a more valid approach in both a clinical and practical domain when investigating red misnaming as the colours and luminous intensities in the workplace are replicated in the signal. Use of the RLLT involves the prevailing signalling practices, accepted responses of the RLLT involve only red, yellow, green and absence of a signal both as stimuli and responses. In addition, in the previous studies [3, 4] the subjects were presented with single signal lights where suburban signalling practices is mostly to use double lights. It has long been the practice to design lanterns with two lights [19] or even three. [20] Performance is affected by the number of lights presented. [21] Bangerter filters (Reyser Optik AG, St. Gallen, Switzerland) are translucent stippled plastic filters used to degrade image quality in the treatment of amblyopia. Bangerter filters act more like a Gaussian filter with which there is monotonically increasing contrast reduction of higher spatial frequencies. [22] The effects of Bangerter filters on colour vision have also not been investigated previously but may be useful to assess colour perception when contrast is reduced without the effect of chromatic aberration, such as occurs in the presence of ocular pathology. The spectral transmittance (direct and diffuse) of the Bangerter filters used were measured using Cary 5000 dual beam and the performance assess using the criteria of the standards relating to coloration limits for clinical observation. [23–25]. These are much more stringent requirements than the coloration requirements for traffic signals in eye protection .(e.g. [26]). As an illustration of this neutrality of spectral transmittance, blue-blocking lenses, which have a slightly visible tint, have been shown to have no statistically significant effect on colour discrimination [27] and also to comply with these clinical observation coloration requirements. [23] As a consequence, any colour contingent effects of the Bangerter filters are not an inherent property of the filters. Methods Subjects Participants were recruited via email to the School of Optometry and Vision Science, University of New South Wales, Sydney by the program coordinator and utilising notice boards around the university facilities. The study and recruitment process were conducted with ethics approval from the UNSW Human Research and Ethics advisory board. The ethics approval number was HC220196. The inclusion criteria to be included in this study comprise: age 19–59, best corrected visual acuity was no worse than 6/9 binocularly (being the requirement in the railway medical requirements), healthy eyes with no current or active ocular conditions and sufficiency in English. The exclusion criteria were age range outside of 19–59 (being within the working age ranges for locomotive drivers) and a colour vision deficiency (being a requirement for locomotive drivers). Experienced railway employees were not included in the criteria as a previous study has shown that naive subjects and railway workers performed equally well on the RLLT. [13, 16, 17] Additionally, at the time of recruitment to this study, it was advised that recruitment of railway employees was not an option due to the industrial action at the time on NSW Railways. (Casolin, A. personal communication). Participants were made aware of the procedures involved in the study and inclusion and exclusion criteria before signing a participant information and consent form prior to undertaking both screening and study. Screening A screening process was required to determine eligibility to participate in the study. This included normal colour vision status, subjective refraction and best corrected visual acuity, and ocular health assessment. To screen participants for a colour vision deficiency, participants needed to pass, ≤ 3 errors on the screening plates of a 1996 edition 24-plate Ishihara colour vision test administered under a Phillips fluorescent tube source type 965 (Phillips, Eindhoven, Netherlands). This source has a CIE general colour rendering index ≥ 90 and a nominal correlated colour temperature of 6500 K consistent with recommendations. [28, 29] They were further required to have an anomalquotient in the range 0.8–1.2 and a matching range ≤ 5 scale units on the Neitz Model OT anomaloscope (Neitz Instruments Co Ltd., Tokyo, Japan). This anomaloscope complied with the recommendations for Rayleigh equation anomaloscopes. [28, 30, 31] A full subjective refraction was performed to obtain the patient’s refractive error and best corrected visual acuity. Ocular health assessment was assessed using fundus photography with the iCare DRPlus (iCare Linland Oy, Vantaa, Finland) to examine the posterior pole. Procedure The Railway Lantern LED Test (RLLT) (ART Electronics, Sydney, Australia) was administered at 6 m, the specified test distance for locomotive drivers. [18] At 6m, the task represents that of a high-speed country train driver who must detect and recognise a signal at, at least, the necessary stopping distance of 1600m. [13] The test presents 24 pairs of signals that are vertically aligned and each shown, automatically, for 2.1 ± 0.1 s. The colours and luminous intensities are representative of NSW railway practices. Accepted responses for each signal were “red”, “yellow”, “green” or “no signal”. The order in which the signal pairs were presented was randomised. In the clinical application of the test, the signal pairs are at a fixed location and normally administered from 1 to 24 or 24 to 1. The order of unblurred and blurred presentation sets were randomised. The lantern used was recalibrated annually in an ISO/IEC 17025 [32] accredited laboratory, as required at the time by Transport for NSW. In order to mask the presentation order and prevent memorisation, the RLLT was mounted on wheels to allow lateral movement and placed behind a black cardboard aperture as shown in Fig. 1 . This allowed only a single presentation pair to be seen at a constant location. The rest of the instrument was obscured so that the position of the signal pairs in the array could not be determined. The luminance of the surround was < 1 cd.m -2 . Test conditions The RLLT was administered under five viewing conditions binocularly using trial lenses in a trial frame adjusted to the subject’s distance inter-pupillary distance and set vertically so that they viewed though the centre of the lenses to avoid prism by decentration and lateral chromatic aberration effects. The five viewing conditions were; Best corrected refraction add + 0.50 DS binocularly add + 0.75 DS binocularly add Bangerter filter 1.0 add Bangerter filter 0.8 Conditions 2 and 3 involved an adjustment of + 0.50DS and + 0.75DS in the trial frame (i.e. the power of the trial frame lenses was changed such that there was only one spherical and one cylindrical lens, to avoid the interreflections and transmission losses that extra surfaces would cause. The Bangerter filters for conditions 4 and 5 were adhered to flat glass goggle lenses that were worn over the top of the trial frame. The best corrected refraction was used as a control. +0.50 DS and + 0.75 DS were chosen to include the viewing conditions of Wood et al. [3, 4] Bangerter filters 1.0 and 0.8 were chosen after a pilot study showed that the 0.6 filter and lower were too visually degrading and resulted in an inability to do the test at all. The higher levels of refractive blur used in the previous study [4] were also omitted to reduce the demand on the subjects and because they would reduce visual acuity well below that required in the medical standards. [18] Procedure All procedures were performed at the Colour Vision Clinic of the University of New South Wales. The prevailing COVID-19 hygiene protocols were followed. Visual acuities were measured without and with Bangerter filters 1.0 and 0.8. Contrast sensitivity was measured binocularly using the MARS test (Mars Perceptrix Corporation, Chappaqua, NY, USA) with best corrected refraction followed by added Bangerter filters. The RLLT was administered according to the instruction manual with the participant seated 6 m from the instrument in a normally lit room (300 lux) without significant glare and no visible windows. Ambient lighting has been shown to have no effect on the results of the Farnsworth lantern. [33] They were instructed: “You will be shown a pair of lights, one above the other for two seconds. I want you to tell me what colours you see. Tell me the top one first. The only colours you will be shown are red, yellow and green and these are the only colour names that you can use. In some cases there is only one light, in which case respond, “no light”, again in the order of top first, then bottom.” Breaks were given after each test to minimise patient fatigue. “Red-signal related errors” were defined as incorrect responses involving the signal red. These included any missed red, red reported as yellow and red reported as green. The outcome for red-signal related errors was the proportion of the total number of red presentations. Results A total of 20 participants completed the study. Table 1 provides participant demographics Table 2 provides details of visual acuity in the five states. The subjects all had better than 6/9 visual acuity, the worst being one case of 6/6 − 1. Table 1 Demographics of the study participants (mean ± 1 standard deviation). Characteristic Value (mean ± 1 s) Age (years) 22.4 ± 1.1 Gender Male, n (%) 10 (50) Female, n (%) 10 (50) Table 2 Visual acuity of the participants. Best corrected Bangerter Refractive blur 1 0.8 0.50 D 0.75 D Mean -0.11 0.05 0.23 0.17 0.30 SD 0.06 0.09 0.14 0.08 0.10 median -0.10 0.05 0.23 0.18 0.31 1st quartile -0.12 -0.02 0.14 0.09 0.21 3rd quartile -0.08 0.10 0.30 0.23 0.38 Skewness -0.11 0.37 0.40 0.35 0.42 Absolute values of skewness ≤ 1.0 indicate a normal distribution. [34] Figure 2 shows the relationship between number of errors made naming red, LogMAR visual acuity and Bangerter induced blur, as an example. Table 3 lists the Peason correlation coefficients for each level of blur and the significance of the value. The same analysis has been carried out on the yellow and green errors. There were no significant relationships found between number of errors made and visual acuity within the three induced blur levels of each blur type but there was a significant relationship, p < 0.01, for the pooled data between errors made and visual acuity. Table 3 Correlation coefficients for the relationship between visual acuity and number of red naming errors for each blur type and for the results as a whole Red errors No blur B 0.8 B 0.6 All Correlation 0.327 0.420 0.107 0.745 Significance p > 0.05 p > 0.05 p > 0.05 p < 0.01 This analysis was then carried on both types of blur and for each colour. No significant relationship was found within blur levels and types. For the pooled data, the results are set out in Table 4 Table 4 Correlation coefficients and significance for the relationship between number of naming errors and visual acuity for each blur type. Errors per subject Blur type Red Yellow Green Bangerter 0.745 -0.074 0.546 p < 0.01 ns p < 0.01 Refractive 0.288 -0.088 0.375 0.01 < p < 0.05 ns p < 0.01 Figure 3 shows the proportion of errors made on each of the signal colours, these comprise all the errors for each signal colour, that is, signal misnamed or not seen. The responses where the subject reported a colour when none were present are not included. This error occurred only once in the unblurred state, 3 subjects each made 1 error in each of the refractive blur states, there were no errors in the lesser non-refractive blur state and 2 subjects made an error and a subject made 3 errors in the greater non-refractive blur state. Figure 4: Relationship between mean LogMAR visual acuity and mean red signal errors for non-refractive (Bangerter filter) and refractive blur. Error bars are ± 1 standard error in proportion of errors and visual acuity. The Y error bars may be smaller than the symbol. Figure 4 shows the breakdown of red signal related errors, that is when a red signal is missed or red miscalled as yellow or green. Errors occurred far more often with red than yellow or green ( p < 0.0001) and with Bangerter filter blur more than refractive blur ( p < 0.0001). Failing to see a red signal rather, than misnaming the red as yellow or green, was the most predominant error (p < 0.0001) and far more easily induced by Bangerter filter than refractive blur ( p < 0.0001) and is a lot less common than miscalling red as yellow (p < 0.0001). (Paired t-tests) Discussion The predominant effect of both types of blur is to cause the observers to miss the red signals rather than misname them. While miscalling red as yellow is the second most common error, it is very much less frequent than failing to see the red. The previous studies [3, 4] used both bright and dim backgrounds, with different mis-naming rates. The conditions in the current experiment are probably intermediate between previous conditions. In addition, the second clear effect is that the Bangerter filters, despite causing less loss in visual acuity than refractive blur, give rise to more colour naming errors of all types. This may be seen by comparing the filled and unfilled symbols in Fig. 3 . Bangerter filters also give rise to more scattered light than ophthalmic lenses (see appendix), so that the less immediate background of the room lit to 250 lx maybe more effective in masking the signals. The results show that responses with refractive blur show fewer errors than the bright surrounds of the previous studies, where a significant effect of refractive blur on the miscalling of red as “orange-yellow” was reported. While the authors wrote about red looking yellow, the actual experiments did not permit the use “yellow” alone as a descriptor. The classical studies of colour naming have shown theoretically [35] and in practice [36] that, given the choice of colour names of red, orange and yellow, wavelengths longer than about 605 nm were never called “yellow” and shorter than 605 nm were never called “red”. The introduction of the option of “orange” creates considerable overlap, such that around 620 nm is called ”red” and “orange” approximately equally frequently and around 570 nm called “yellow” and “orange” equally frequently. The distinction is less clear for “low intensity” stimuli. [36] Holmes [9] collected but did not report data on orange. He reports that “Experiments in the differentiation between yellow and orange showed considerable confusion between these colour names at low illuminations”. Soon & Cole [37] did not use the response “orange” either. In addition, their Red 2 and Red 3, see their Table II, are too orange (y > 0.292) to comply with the prevailing requirements [8] for wayside signals although they do comply with the requirements for highway/rail crossing (being the same as for traffic signals generally [38, 39]). Red 1 was never called “yellow” by young or old subjects. Similarly, Yellow 2 and Yellow 3 are too green to comply (y > 0.430). So there is blurred borderline between red and orange and between yellow and orange that does not exist between yellow and red. In the earlier studies, [4] the option to report a signal as not seen was not provided, although in the earlier of the two studies, this was reported as a response but not analysed. The problem here is that, if a signal is not seen, then the subject will be required to guess and will choose a response at random. So, half the time a failure to see a signal will result in a two alternative forced-choice response of the wrong colour. Thus, mis-calling of red as “orange-yellow” would have occurred 50% of the time that the signal was not seen. Since the yellow has about twice the luminous intensity of the red in their experiments, not seeing the yellow will occur significantly less often. In the current study, participants were given options between “red”, “yellow”, “green” or “no light”. This is reflective of signalling practices and represents the task that train drivers are given and reds that are not seen will not be called “yellow-orange”. A second reason as to why reds were less likely to be miscalled as yellow in this study, if the effects are related to chromatic aberration, could be due to the narrower band spectral distributions of the LED lights in the RLLT. The narrower spectral bandwidth of LEDs compared with incandescent signals with a broad band filter is well illustrated in Fig. 1 of the earlier previous study as is the narrower spectral distribution of the interference filter. [3] The authors do not separate the responses for the broad band and narrow band red other than qualitative comments on than anomalous results of three observers. It may also be seen in the traffic signals used in the ISO test method standard for eye and face protection, [40] see Fig. 5 . These data were collected in the Optics & Radiometry Laboratory, UNSW (ORLAB). Thus any chromatic aberration effects [41, 42] may be different for the two types of signal. The phenomenon was originally described [3] as occurring when signals were blurred because they were viewed through the intermediate corridor of a progressive lens, although it was noted that blur in general also gave rise to the observation. The authors discounted “chromatic aberration” as an explanation because it was in the wrong direction to explain the results since red is focussed, in the refractively blurred condition, closer to the retina not further away. This argument assumes focus is accurate without any leads of accommodation as would occur for example in darker environments in a phenomenon known as empty field myopia. [43] Wood et al’s argument implicitly addressed longitudinal chromatic aberration but they were not specific. [3] As an anecdotal comment, some years ago a request for resolution of a complaint came to the ORLAB which is the only testing laboratory in Australia that is ISO/IEC 17025 [32] accredited to test to the eye and face protection standards. The complaint related to two prescription eye protectors that were supposed to be identical but the newer pair caused the wearer to see coloured fringes and the older pair did not. Both pairs were the same material (polycarbonate), the same design of progressive lens, the same distance prescription and near addition, the same frame, the same base curves and the same centration distances. What was identified as the only difference was that the newer pair had prism thinning applied in manufacture. This is a process in which equal vertical prisms are worked on the two lenses to reduce the thickness and make the lenses lighter and minimise edge thickness around the superior edge. Polycarbonate is widely used in eye protection being the most impact resistant of the lens materials. [44] Complaints about coloured fringes, especially associated with higher refractive powers, are, anecdotally, relatively common with polycarbonate given that it has the lowest Abbe number of all the ophthalmic lenses (30 compared with 58 for hard resin, allyl glycol carbonate). As a consequence, the phenomenon originally described by Wood et al [3] may be related to lateral chromatic aberration from the prism and the blur effect may be coincidental. The actual colours and luminous intensities of the RLLT stimuli are considered commercial in confidence but they were chosen to comply with CIE S 004. [45] See Fig. 6 . The CIE limits are a little more liberal in the green direction than the ARTC limits [7] but the colours used in the previous study [4] would comply. However, also shown are the yellow limits for traffic signals in Australia. [38] These may be seen to be much more restrictive in the red direction compared with both the CIE and ARTC. So the subject group will comprise people who are familiar with the less orange road traffic signals, which may influence their use of the term “orange-yellow”. The luminous intensities of the stimuli in the RLLT were deliberately varied to reflect the real-life situations where the viewing distances may vary and the observer may not be in the direction of the maximum intensity. While the actual specifications of the signals are considered commercial in confidence, they were derived after making measurements on all the models of signal made available by Railcorp NSW at the time. It is fair to say that they will on average, be significantly lower than the stimuli in the Wood et al study. [4] The use of Bangerter filters was implemented in this study to investigate whether longitudinal chromatic aberrations are involved in the colour misperception effect. Bangerter filters do not refract light but behave more like a Gaussian filter thus longitudinal chromatic aberrations cannot be induced. A study by Gupta et al [41] demonstrated that longitudinal chromatic aberrations and not monochromatic aberrations may be linked with the colour misperception phenomenon. This effect is also not affected by L/M cone ratio. They also proposed that an additional defocus dependent neural mechanism may also contribute to change in colour appearance. [45] Hence, the presence of missed reds and reds called yellow are indicative that factors other than longitudinal chromatic aberration may be inducing a colour misperception effect. The presence of red misperceptions with the Bangerter filters in this study raises the question as to whether a non-optical defocus mechanism is involved. The errors made by participants under best corrected conditions are anomalous in that 2 participants (10%) failed the RLLT. In the development study, [13] 106 colour vision “normals”; only one (0.9%) individual failed. At the time, a pass on the RLLT constituted less ≤ two misnamings, ≤ one green or yellow missed and ≤ one blank named as a colour. In the commercially available version and based on a decision by RailCorp NSW (now incorporated into Transport for NSW), any missed or miscalled reds constitute a fail. However, in an experimental domain, naive participants may not invest sufficiently to avoid making judgement errors. This is known as the mutable-zero effect in risky choices. [46] There are probably many factors leading to the occurrence of a SPAD. These could be due to a signal being missed, being misperceived or some other factor. There does not seem to have been any consideration of this issue in any of the studies of causes of SPADs. In the case of the NSW railways, the investigation of SPADs does not include direct questions about whether the signal was not seen or seen as yellow (Casolin, A. personal communication) and there are no reports from other jurisdictions to be found. As a consequence, the hypothesised [4] association between SPADs must be seen as very tentative at this stage. At the time of the first Wood et al study [3], the manufacturing standard on prescription eye protection, AS/NZS 1337.6 [47] was yet to be published and the conventional wisdom was that polycarbonate was the material of choice for medium impact occupational eye protection. “Medium impact” in AS/NZS 1337 was the same, at the time of Wood et al [3] as “low energy impact” in EN 166:2001 [48] and “high velocity impact” for spectacle type eye protectors in ANSI Z87.1:2003 [49]. Since that time, other lens materials for this level of impact protection have come in to use. While polycarbonate remains the most impact resistant material, [50] there are other materials (most notably polyurethane, introduced in 2001) that do comply with the medium impact requirements, have a lower refractive index and a higher Abbe number than polycarbonate. So, if the coloured fringing is an issue, there is, these days, an alternative solution. Conclusions Rather than a colour misperception, the errors seem to be more related to simply missing the signal. This current study does find that low refractive blur and non-refractive blur does cause red, more than yellow or green, to be missed rather than misnamed. This study also shows that non–refractive blur is a more potent means of inducing error in colour detection and, to a lesser extent, recognition in a simulated practical test. There are several methodological reasons why this study gives different results from the earlier studies [3] given the difference in the stimuli and, especially, in the responses required of the experimental subjects. It was been suggested that stray light and the Abney effect could [3, 4] play a role in the misnaming since the desaturation of red leads to an increased likelihood of naming as yellow. Thus the bright surround was associated with the error which did not occur. Adaptation is also affected and affects colour naming is a complex way. [51] The test conditions in this study would lead to an adaptation level that is intermediate between the bright and dark surround of the previous study.. In addition, Bangerter filters have been shown to be “qualitatively different” from defocus blur and “do not exhibit spurious resolution and phase shifts, as does defocus” with grayscale stimuli. [52] Given that the RLLT is a simulated practical test, the results of this study suggest that the conclusions of the original observations [3, 4] of miscalling red as “yellow” having practical consequences may be overstated. Until the post-SPAD de-briefing questions include the differentiation of “red signal not seen” and “red signal not perceived as red” the link is unlikely to be resolved. Even though the Goodwell OK collision [53] involved a SPAD and the vision and colour vision of the engineer were identified as inadequate, the incident involved failing to reduce speed to 40 mph in response to a flashing yellow, failing to reduce speed further to 30 mph in response the yellow over red signals and, finally, failing to stop, or even slow down, at a red signal. Even misperceiving the red as yellow should have led to a slowing of the train. So this collision was preceded by failing to see red and yellow signals with the number of lights being redundant information that should have resulted in a response even if the colour was misperceived. Since the medical standards [18] also include a requirement for visual acuity (6/9 in the better eye), this may be an indirect way of minimising this issue in practice. The extent to which the results, from a young population, may be extrapolated to older observers is not known but Soon and Cole [37] showed no age effect in the recognition of Red 1 (the only rail use compliant red). Declarations Disclosure Statement The authors report there are no competing interests to declare. data availablity The data that support the findings of this study are available from the corresponding author, [SJD], upon reasonable request. Funding statement This project did not receive any funding. Author Contribution JC and TN carried out the data collection, literature search, initial data analysis and first draft of project report. They assisted in the ethics application.MB assisted with method design and ethics application, oversaw the data collection, provided the major revision of the first data analysis and reviewed drafts of the paper and responses to reviewers. VH assisted with method design and ethics application, oversaw the data collection and reviewed drafts of the paper and responses to reviewers. .SD provided the concept of the project, first draft of the method, ethics application, oversight of the data collection, further data analysis, drafting of the report into the paper and preparation of the revisions and responses to reviewers Acknowledgement To Dr Armand Casolin, Chief Health Officer, Safety, Environment & Regulation, Transport for NSW for his advice. To the staff of ORLAB, UNSW for the use of the instruments and assistance with the spectral transmittance and haze measurements. To the reviewers (especially reviewer 1) who helped make it a better paper. Data Availability The data that support the findings of this study are available from the corresponding author, [SJD], upon reasonable request. References Nikandros G, Tombs D. Measuring Railway Signals Passed At Danger. In: Cant T, editor. 12th Australian Conference on Safety Critical Systems and Software. Adelaide: Conferences in Research and Practice in Information Technology (CRPIT); 2007. p. 41-6. http://www.ntsb.gov/investigations/AccidentReports/Reports/RAR1302.pdf Rail Safety and Standards Board. Annual Safety Performance Report 2012/13. London.: Rail Safety and Standards Board; 2013. https://www.worldtransitresearch.info/research/4859/ Wood JM, Atchison DA, Chaparro A. When Red Lights Look Yellow. Invest Ophth Vis Sci. 2005;46 (11):4348-52. https://doi.org/10.1167/iovs.04-1513. Wood JM, Atchison DA, Black AA, G.S. L. Low levels of refractive blur increase the risk of colour misperception of red train signals. Ophthalmic Physiol Opt. 2022;42:872-8. https://doi.org/10.1111/opo.12979. Naweed A, Trigg J, Cloete S, Allan P, Bentley T. Throwing good money after SPAD? Exploring the cost of signal passed at danger (SPAD) incidents to Australasian rail organisations. Saf Sci. 2018;109:157-64. https://doi.org/10.1016/j.ssci.2018.05.018. van der Flier H, Schoonman W. Railway signals passed at danger: Situational and personal factors underlying stop signal abuse. Appl Ergon. 1988;19(2):135-41. https://doi.org/10.1016/0003-6870(88)90006-3. ARTC. Light Signals. SPS 11 - (RIC Standard: SC07 1000 00SP). Australian Rail Track Corporation Limited; 2005. ARTC. ESA-04-01 Colourlight signals and indicators. Australian Rail Track Corporation Limited; 2024. http://extranet.artc.com.au/docs/eng/signal/procedures/material/ESA-04-01.pdf Holmes JG. Colour recognition of very small light sources. Docum Ophthalmol. 1949;3(1):240-50. https://doi.org/10.1007/BF00162605. Topley H. Sight testing for the merchant navy. 16:36-47. B J Physiol Opt. 1959;16:36-47. Cole BL, Vingrys AJ. Who fails lantern tests?. Doc Ophthalmol. 1983;55 (3):9. https://doi.org/10.1007/BF00140807. International Maritime Organisation. Conventions on the International Regulations for Preventing Collisions at Sea. (COLREGs). London: International Maritime Organisation; 1972. https://www.imorules.com/COLREG90_RULES.html Dain SJ, Casolin A, Long J, Hilmi MR. Color vision and the railways: Part 1 The Railway LED Lantern Test. Optom Vis Sci. 2015;92(2):138-46. https://doi.org/10.1097/OPX.0000000000000460. Vingrys AJ, Cole BL. Validation of the Holmes-Wright lanterns for testing colour vision. Ophthal Physiol Opt. 1986;3 (2):16. https://doi.org/10.1111/j.1475-1313.1983.tb00593.x. Farnsworth D, Foreman P. Development and trial of New London Navy Lantern as a selection test for serviceable color vision. Groton, CT, USA: Naval Submarine Medical Research Laboratory; 1946. Dain SJ, Casolin A, Long J. Color vision and the railways: Part 2. Comparison of the CN Lantern used on the Canadian Railways and Railway LED lantern tests. Optom Vis Sci. 2015;92(2):147-51. https://doi.org/10.1097/OPX.0000000000000461. Dain SJ, Casolin A, Long J. Color Vision and the Railways: Part 3. Comparison of FaLant, OPTEC 900, and Railway LED Lantern Tests. Optom Vis Sci. 2015;92(2):152-6. https://doi.org/10.1097/OPX.0000000000000462. National Transport Commission. National Standard for Health Assessment of Rail Safety Workers. Melbourne: National Transport Commission; 2024. https://www.ntc.gov.au/sites/default/files/assets/files/Rail%20Standard%202024.pdf Cole BL, Vingrys AJ. A survey and evaluation of lantern tests of color vision. Am J Optom Physiol Opt. 1982;59 (4):9. https://doi.org/https://journals.lww.com/optvissci/abstract/1982/04000/A_Survey_and_Evaluation_of_Lantern_Tests_of_Color.9.aspx. Hovis JK, Oliphant D. A lantern color vision test for the rail industry. Am J Indust Med. 2000;38 (6):681-7. https://doi.org/10.1002/1097-0274(200012)38:63.0.CO;2-4. Neubert FR. Colour vision in the consulting room. Br J Ophthalmol. 1947;31:275-88. https://doi.org/10.1136/bjo.31.5.275. Odell NV, Leske DA, Hatt SR, Adams WE, Holmes JM. The effect of Bangerter filters on optotype acuity, Vernier acuity, and contrast sensitivity. J AAPOS. 2008;12:555-5590. https://doi.org/10.1016/j.jaapos.2008.04.012. Dain SJ, Hovis JK, Hoskin AK. The specification of color limits in eye protection lenses for use when color-contingent clinical observations are made. Color Res Appl. 2022;47:1118-33. https://doi.org/10.1002/col.22795. AS 16321-4 (Int) Eye and face protection for occupational use Protection against biological hazards. Sydney: Standards Australia; 2023. ISO 12609-1 Eye and face protection against intense light sources used on humans and animals for cosmetic and medical applications Part 1: Specification for products. Geneva: International Organization for Standardization; 2021. ISO 12312-1 Eye and Face protection— Sunglasses and related eyewear - Part 1: Sunglasses for general use. Geneva: International Organization for Standardization; 2022. Baldasso M, Roy M, Boon MY, Dain SJ. Effect of blue–blocking lenses on colour discrimination. Clin Exp Optom. 2021;104(1):56-61. https://doi.org/10.1111/cxo.13139. National Research Council. Procedures for Color Vision Testing. Report of the Working Group 41. Washington, DC: Committee on Vision. Assembly of Behavioral and Social Sciences. National Research Council. National Academy Press; 1981. https://pubmed.ncbi.nlm.nih.gov/25032450/ Dain SJ, Atchison DA, Hovis JK, Boon M-Y. Lighting for color vision examination in the era of LEDs: the FM100Hue Test. J Opt Soc Am A. 2020;37(4):A122-A32. https://doi.org/10.1364/JOSAA.382301. Dain SJ, Hovis JK. Recommendations and requirements for the wavelengths in Rayleigh equation anomaloscopes. J Opt Soc Am A. 2023;40(3):A121-A9. https://doi.org/10.1364/JOSAA.477144. ISO 5868 Ophthalmic optics and instruments — Anomaloscopes for the diagnosis of red-green colour vision deficiencies. Geneva: International Organization for Standardization; 2025. ISO/IEC 17025 General requirements for the competence of testing and calibration laboratories. Geneva: International Organization for Standardization and International Electrotechnical Commission; 2019. Dain SJ, Honson V, Ang J. The effect of two lighting conditions on performance of the Farnsworth Lantern color vision test. Aviat Space Environ Med 1988;59 (4):3. https://doi.org/https://asma.kglmeridian.com/downloadpdf/view/journals/asem/59/4/article-p371.pdf. Mishra P, Pandey CM, Singh U, Gupta A, Sahu C, Keshri A. Descriptive Statistics and Normality Tests for Statistical Data. Ann Card Anaesth. 2016;22:67-72. https://doi.org/10.4103/aca.ACA_157_18. Graham CH. Sensation and perception in an objective psychology. Psych Rev. 1958;65(2):65-76. https://doi.org/10.1037/h0046960. Beare AC. Color-name as a function of wavelength. Am J Psychol. 1963;76(2):248-56. https://doi.org/https://www.jstor.org/stable/1419161. Soon FC, Cole BL. Did the CIE get it right? A critical test of the CIE color domains for signal lights. Color Res Appl. 2001;26(2):109-22. https://doi.org/10.1002/1520-6378(200104)26:2%3C109::AID-COL1002%3E3.0.CO;2-Z. AS 2144 Traffic Signal lanterns. Sydney: Standards Australia; 2023. ISO 16508 (CIE S 006.1:1998) Road Traffic Lights — Photometric Properties of 200 mm Roundel Signals. Geneva: International Organization for Standardization; 1999. ISO 18526-2 Eye and face protection – Test methods – Part 2: Physical optical properties. Geneva: International Organization for Standardization; 2020. Gupta P, Atchison DA, Zele AJ, Guo H. The effect of optical aberrations on the colour appearance of small lights. J Vis. 2008;8(17):43. https://doi.org/10.1167/8.17.43. Gupta P, Guo H, Atchison DA, Zele AJ. Effect of optical aberrations on the color appearance of small defocused lights. J Opt Soc Am A 2010;27(5):960-7. https://doi.org/10.1364/JOSAA.27.000960. Westheimer G. Accommodation measurements in empty visual fields. J Opt Soc Am. 1957;47(8):714-8. https://doi.org/10.1364/JOSA.47.000714. Dain SJ. Materials for occupational eye protectors. Clin Exp Optom. 2012;95 (2):129-39. https://doi.org/10.1111/j.1444-0938.2012.00704.x. CIE S 004 Colours of light signals. Vienna: Commission Internationale de l’Éclairage; 2001. Scholten M, Read D, Stewart N. The framing of nothing and the psychology of choice. J Risk Uncertain. 2019;59:125-49. https://doi.org/10.1007/s11166-019-09313-5. AS/NZS 1337.6 Personal eye protection Part 6: Prescription eye protectors against low and medium impact. Sydney: Standards Australia/Standards New Zealand; 2007. CEN. EN 166 Personal eye-protection - Specifications. Brussels: Comité Européen de Normalisation (CEN); 2001. ASSP/ANSI Z87.1 American National Standard for Occupational and Educational Personal Eye and Face Protection Devices. Park Ridge, IL: American Society of Safety Professionals; 2003. Chou BR, Yuen GS, Dain SJ. Ballistic impact resistance of selected organic ophthalmic lenses. Clin Exp Optom. 2011;94 (6):568-74. https://doi.org/10.1111/j.1444-0938.2011.00651.x. Webster MA. Human colour perception and its adaptation. Netw: Comput Neural Syst. 1996;7(4):587-634. https://doi.org/10.1088/0954-898X_7_4_002. Pérez, GM, Archer SM, Artal P. Optical Characterization of Bangerter Foils. Invest Ophthalmol Vis Sci. 2010;51:609-613. https://doi.org/10.1167/iovs.09-3726. National Transportation Safety Board. Head-On Collision of Two Union Pacific Railroad Freight Trains Near Goodwell, Oklahoma June 24, 2012. NTSB/RAR-13/02 PB2013-107679. Washington, DC.: National Transportation Safety Board; 2013. http://www.ntsb.gov/investigations/AccidentReports/Reports/RAR1302.pdf AS 16321.4. (INT) Eye and face protection for occupational use Part 4: Protection against biological hazards. Sydney: Standards Australia; 2023. ISO 14782 Plastics - Determination of haze for transparent materials. Geneva: International Organization for Standardization; 2021. ASTM International. D1003-11 Standard Test Method for Haze and Luminous Transmittance of Transparent Plastics. West Conshohocken, PA: ASTM International; 2011. Additional Declarations No competing interests reported. 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No blur, Bangerter 0.8 and 0.6 results are shown as circles, square and diamond symbols, respectively. The linear regression lines are shown as dotted, dashed and dot-dash lines, respectively and the linear regression line for the combined values is a solid line.\u003c/p\u003e","description":"","filename":"2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-8052714/v1/9733cb34574b2cfd9e728d78.jpg"},{"id":96654106,"identity":"84e7223d-f31e-4545-bcc4-c30fd6bb7b79","added_by":"auto","created_at":"2025-11-24 16:40:13","extension":"jpg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":60712,"visible":true,"origin":"","legend":"\u003cp\u003eRelationship between mean LogMAR visual acuity and mean colour naming errors for each signal colour and non-refractive (Bangerter filter) and refractive blur. Error bars are ± 1 standard error in proportion of errors and visual acuity. The Y error bars may be smaller than the symbol.\u003c/p\u003e","description":"","filename":"3.jpg","url":"https://assets-eu.researchsquare.com/files/rs-8052714/v1/78f4f04f47643e4995719e68.jpg"},{"id":96710065,"identity":"c0fd0ddd-2f9e-478a-be41-8ca3e7efbd48","added_by":"auto","created_at":"2025-11-25 10:10:01","extension":"jpg","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":64179,"visible":true,"origin":"","legend":"\u003cp\u003eRelationship between mean LogMAR visual acuity and mean red signal errors for non-refractive (Bangerter filter) and refractive blur. Error bars are ± 1 standard error in proportion of errors and visual acuity. The Y error bars may be smaller than the symbol.\u003c/p\u003e","description":"","filename":"4.jpg","url":"https://assets-eu.researchsquare.com/files/rs-8052714/v1/f5d160b566a09dcc4d317f37.jpg"},{"id":96654112,"identity":"b9ddb7eb-4e89-4e6e-a534-7051ab00507a","added_by":"auto","created_at":"2025-11-24 16:40:13","extension":"jpg","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":50709,"visible":true,"origin":"","legend":"\u003cp\u003eRelative spectral luminous energy of incandescent and LED traffic signals. The values have been equalised for total luminous energy. Data from ISO 18526-2:2020, Annex D. [40]\u003c/p\u003e","description":"","filename":"5.jpg","url":"https://assets-eu.researchsquare.com/files/rs-8052714/v1/9d10c6670650b33429d91972.jpg"},{"id":96709487,"identity":"7951fcb8-ec5c-401e-b291-1d979cee7342","added_by":"auto","created_at":"2025-11-25 10:09:06","extension":"jpg","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":38121,"visible":true,"origin":"","legend":"\u003cp\u003eChromaticity Diagram according to 1931 C.I.E Coordinate System showing for yellow LED Lights. The limits set by the CIE, [45] ARTC7 and the Australian traffic signal standards. [38]\u003c/p\u003e","description":"","filename":"6.jpg","url":"https://assets-eu.researchsquare.com/files/rs-8052714/v1/08703b858ff541658f9f6d23.jpg"},{"id":96712771,"identity":"875877b0-2195-4d3d-a3b2-58407ef11647","added_by":"auto","created_at":"2025-11-25 10:16:36","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":884364,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8052714/v1/0b85c924-6538-4e24-8625-72a81e3a6a81.pdf"},{"id":96654101,"identity":"4137e1ef-61c3-43da-9445-fe0befdfc3d9","added_by":"auto","created_at":"2025-11-24 16:40:13","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":18374,"visible":true,"origin":"","legend":"","description":"","filename":"Appendix.docx","url":"https://assets-eu.researchsquare.com/files/rs-8052714/v1/34009a726baf9eb029b2390c.docx"}],"financialInterests":"No competing interests reported.","formattedTitle":"LED railway signal detection rather than recognition is affected by both refractive and non-refractive blur","fulltext":[{"header":"Introduction","content":"\u003cp\u003eSignals passed at danger (SPAD) are events where a train passes a stop signal without authority. [1, 2] Previous research has reported refractive defocus as being a significant factor in signal recognition that can occur when looking through low added power lenses, such as the corridor of progressive addition lenses (PALs). [3, 4]\u003c/p\u003e\u003cp\u003eA survey of Australian and New Zealand rail organisations found that SPADs occur up to 62 times annually resulting in associated delays averaging 270 minutes costing \u003cspan\u003e$\u003c/span\u003e153,000 and are accompanied by preventative and reactive costs of up to \u003cspan\u003e$\u003c/span\u003e520,060 and \u003cspan\u003e$\u003c/span\u003e1.87\u0026nbsp;million annually respectively. [5] A previous study in the 1980s reported no significant situational or personal factors underlying 224 SPADs events in the Netherlands. [6] Weather and adverse conditions such as darkness, rain and fog did not contribute to SPADs. These events were however more frequent in the morning, particularly 4\u0026ndash;9 am, and at the start of locomotive drivers\u0026rsquo; duty periods. The authors alluded to fatigue as possibly being the major factor. Drivers committing SPADs also had lower reaction scores on a multi-choice reaction test and less occupational satisfaction.\u003c/p\u003e\u003cp\u003eThe effects of optical defocus on rail signals misperception were studied after a report of red signals appearing orange-yellow when viewed at long distances through progressive additional lenses (PALs). Studies by Wood et al. [3, 4] found a significant percentage of red signals reported as appearing orange-yellow in the presence of a bright background or glare source and at longer distances through spherical refractive blur in both field and laboratory environments. The follow-up study [4] involved a change in protocol testing using signals satisfying the Australian Rail Track Corporation (ARTC) Engineering standard Light Signals SPS 11 [7] (now superseded by ARTC ESA-04-01 Colourlight signals and indicators [8]) where results were similar. The authors did not use the conventional names of signalling practices as the set responses were a forced-choice of \u0026ldquo;red\u0026rdquo; or \u0026ldquo;orange-yellow\u0026rdquo;. This is not reflective of signalling practices and does not reflect decisions that rail drivers need to make. They did, however, consider their observations to be relevant to the occurrence of SPADs.\u003c/p\u003e\u003cp\u003eHolmes [9] observed that \u0026ldquo;For example, an observer presented with a bluish-green light and asked to call it 'green' or 'not green' would almost certainly call it 'not green' but if asked to call it 'green\u0026rsquo; or 'red', he would call it 'green'. The limits of the area on the chromaticity diagram called 'green' when the choice is 'green' or \u0026lsquo;not green' would be different from those when the choice is 'green' or 'red'. Further, the choice made by the observer will differ according to whether he knows the colour of the light to be one of two or three alternatives, or to whether he is told that the colour may be anything, because in the first problem his decision may be reached by rejecting the alternatives whereas the second problem requires positive recognition of the colour.\u0026rdquo;\u003c/p\u003e\u003cp\u003eAs a consequence, the current research has not reflected modern Australian signalling practices (which are mostly LED) or the prevailing colour naming (red, yellow and green) into their methodology so the practical significance of the observations is unclear.\u003c/p\u003e\u003cp\u003eTopley [10] and Cole \u0026amp; Vingrys [11] report visual acuity effects on performance of the Board of Trade (BoT) Lantern and Holmes-Wright Type B (HWB) lantern, respectively, but the types of misnamings made are not reported. Only one of their 100 subjects had a visual acuity of 6/9. Cole \u0026amp; Vingrys report that the BoT Lantern is a stringent test like the HWB lantern. Since it was designed for maritime use, the HWB uses a colour code of red, green and white and required sighting distances are mainly 6 nautical miles (11.1 km) for white lights and 3 nautical miles (5.6 km) for coloured lights. [12] Railways use red, yellow and green for fixed signals and the critical distance is 1.6 km when locomotive driving. [13] The railways do use red, green and white for their hand-held lanterns. Cole \u0026amp; Vingrys [14] reported that the HWB lantern is more stringent than the Farnsworth Lantern (FALANT),which was also originally developed for naval use and also has a red, green and white code. [15] The FALANT and Railways LED Lantern Test (RLLT) are essentially equivalent in difficulty. [13]\u003c/p\u003e\u003cp\u003eThe current study aims to investigate the effects of both refractive and non-refractive defocus on the detection AND recognition of LED rail signals. This current study uses colours and colour names (red, yellow and green) as used in trackside signalling and using the official colour vision test of the Australian railways.\u003c/p\u003e\u003cp\u003eThe RLLT [13, 16, 17] is a simulated practical test nominated in the Australian National Railway Medical Standards (current version [18]) carried out at a test distance of 6m for those needing to meet normal colour vision standards such as locomotive drivers and at 3m for those needing to detect and recognise coloured signal lights at shorter distances (e.g. station assistants and trackside workers). It is consistent with modern railway signalling practices including the use of the LEDs that are used in signal construction and a range of luminous intensities representative of railway signals in practice. It is possible that the RLLT could be used to identify those at risk of mis-naming red under conditions of defocus. Using the RLLT should be a more valid approach in both a clinical and practical domain when investigating red misnaming as the colours and luminous intensities in the workplace are replicated in the signal. Use of the RLLT involves the prevailing signalling practices, accepted responses of the RLLT involve only red, yellow, green and absence of a signal both as stimuli and responses. In addition, in the previous studies [3, 4] the subjects were presented with single signal lights where suburban signalling practices is mostly to use double lights. It has long been the practice to design lanterns with two lights [19] or even three. [20] Performance is affected by the number of lights presented. [21]\u003c/p\u003e\u003cp\u003eBangerter filters (Reyser Optik AG, St. Gallen, Switzerland) are translucent stippled plastic filters used to degrade image quality in the treatment of amblyopia. Bangerter filters act more like a Gaussian filter with which there is monotonically increasing contrast reduction of higher spatial frequencies. [22] The effects of Bangerter filters on colour vision have also not been investigated previously but may be useful to assess colour perception when contrast is reduced without the effect of chromatic aberration, such as occurs in the presence of ocular pathology. The spectral transmittance (direct and diffuse) of the Bangerter filters used were measured using Cary 5000 dual beam and the performance assess using the criteria of the standards relating to coloration limits for clinical observation. [23\u0026ndash;25]. These are much more stringent requirements than the coloration requirements for traffic signals in eye protection .(e.g. [26]). As an illustration of this neutrality of spectral transmittance, blue-blocking lenses, which have a slightly visible tint, have been shown to have no statistically significant effect on colour discrimination [27] and also to comply with these clinical observation coloration requirements. [23] As a consequence, any colour contingent effects of the Bangerter filters are not an inherent property of the filters.\u003c/p\u003e"},{"header":"Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\u003ch2\u003eSubjects\u003c/h2\u003e\u003cp\u003eParticipants were recruited via email to the School of Optometry and Vision Science, University of New South Wales, Sydney by the program coordinator and utilising notice boards around the university facilities. The study and recruitment process were conducted with ethics approval from the UNSW Human Research and Ethics advisory board. The ethics approval number was HC220196.\u003c/p\u003e\u003cp\u003eThe inclusion criteria to be included in this study comprise: age 19\u0026ndash;59, best corrected visual acuity was no worse than 6/9 binocularly (being the requirement in the railway medical requirements), healthy eyes with no current or active ocular conditions and sufficiency in English. The exclusion criteria were age range outside of 19\u0026ndash;59 (being within the working age ranges for locomotive drivers) and a colour vision deficiency (being a requirement for locomotive drivers). Experienced railway employees were not included in the criteria as a previous study has shown that naive subjects and railway workers performed equally well on the RLLT. [13, 16, 17] Additionally, at the time of recruitment to this study, it was advised that recruitment of railway employees was not an option due to the industrial action at the time on NSW Railways. (Casolin, A. personal communication).\u003c/p\u003e\u003cp\u003eParticipants were made aware of the procedures involved in the study and inclusion and exclusion criteria before signing a participant information and consent form prior to undertaking both screening and study.\u003c/p\u003e\u003c/div\u003e\n\u003ch3\u003eScreening\u003c/h3\u003e\n\u003cp\u003eA screening process was required to determine eligibility to participate in the study. This included normal colour vision status, subjective refraction and best corrected visual acuity, and ocular health assessment. To screen participants for a colour vision deficiency, participants needed to pass, \u0026le; 3 errors on the screening plates of a 1996 edition 24-plate Ishihara colour vision test administered under a Phillips fluorescent tube source type 965 (Phillips, Eindhoven, Netherlands). This source has a CIE general colour rendering index\u0026thinsp;\u0026ge;\u0026thinsp;90 and a nominal correlated colour temperature of 6500 K consistent with recommendations. [28, 29] They were further required to have an anomalquotient in the range 0.8\u0026ndash;1.2 and a matching range\u0026thinsp;\u0026le;\u0026thinsp;5 scale units on the Neitz Model OT anomaloscope (Neitz Instruments Co Ltd., Tokyo, Japan). This anomaloscope complied with the recommendations for Rayleigh equation anomaloscopes. [28, 30, 31] A full subjective refraction was performed to obtain the patient\u0026rsquo;s refractive error and best corrected visual acuity. Ocular health assessment was assessed using fundus photography with the iCare DRPlus (iCare Linland Oy, Vantaa, Finland) to examine the posterior pole.\u003c/p\u003e\n\u003ch3\u003eProcedure\u003c/h3\u003e\n\u003cp\u003eThe Railway Lantern LED Test (RLLT) (ART Electronics, Sydney, Australia) was administered at 6 m, the specified test distance for locomotive drivers. [18] At 6m, the task represents that of a high-speed country train driver who must detect and recognise a signal at, at least, the necessary stopping distance of 1600m. [13] The test presents 24 pairs of signals that are vertically aligned and each shown, automatically, for 2.1\u0026thinsp;\u0026plusmn;\u0026thinsp;0.1 s. The colours and luminous intensities are representative of NSW railway practices. Accepted responses for each signal were \u0026ldquo;red\u0026rdquo;, \u0026ldquo;yellow\u0026rdquo;, \u0026ldquo;green\u0026rdquo; or \u0026ldquo;no signal\u0026rdquo;. The order in which the signal pairs were presented was randomised. In the clinical application of the test, the signal pairs are at a fixed location and normally administered from 1 to 24 or 24 to 1. The order of unblurred and blurred presentation sets were randomised. The lantern used was recalibrated annually in an ISO/IEC 17025 [32] accredited laboratory, as required at the time by Transport for NSW.\u003c/p\u003e\u003cp\u003eIn order to mask the presentation order and prevent memorisation, the RLLT was mounted on wheels to allow lateral movement and placed behind a black cardboard aperture as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. This allowed only a single presentation pair to be seen at a constant location. The rest of the instrument was obscured so that the position of the signal pairs in the array could not be determined.\u003c/p\u003e\u003cp\u003eThe luminance of the surround was \u0026lt;\u0026thinsp;1 cd.m\u003csup\u003e-2\u003c/sup\u003e.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\n\u003ch3\u003eTest conditions\u003c/h3\u003e\n\u003cp\u003eThe RLLT was administered under five viewing conditions binocularly using trial lenses in a trial frame adjusted to the subject\u0026rsquo;s distance inter-pupillary distance and set vertically so that they viewed though the centre of the lenses to avoid prism by decentration and lateral chromatic aberration effects. The five viewing conditions were;\u003c/p\u003e\u003cp\u003e\u003col\u003e\u003cspan\u003e\u003cli\u003e\u003cp\u003eBest corrected refraction\u003c/p\u003e\u003c/li\u003e\u003c/span\u003e\u003cspan\u003e\u003cli\u003e\u003cp\u003eadd\u0026thinsp;+\u0026thinsp;0.50 DS binocularly\u003c/p\u003e\u003c/li\u003e\u003c/span\u003e\u003cspan\u003e\u003cli\u003e\u003cp\u003eadd\u0026thinsp;+\u0026thinsp;0.75 DS binocularly\u003c/p\u003e\u003c/li\u003e\u003c/span\u003e\u003cspan\u003e\u003cli\u003e\u003cp\u003eadd Bangerter filter 1.0\u003c/p\u003e\u003c/li\u003e\u003c/span\u003e\u003cspan\u003e\u003cli\u003e\u003cp\u003eadd Bangerter filter 0.8\u003c/p\u003e\u003c/li\u003e\u003c/span\u003e\u003c/ol\u003e\u003c/p\u003e\u003cp\u003eConditions 2 and 3 involved an adjustment of +\u0026thinsp;0.50DS and +\u0026thinsp;0.75DS in the trial frame (i.e. the power of the trial frame lenses was changed such that there was only one spherical and one cylindrical lens, to avoid the interreflections and transmission losses that extra surfaces would cause. The Bangerter filters for conditions 4 and 5 were adhered to flat glass goggle lenses that were worn over the top of the trial frame. The best corrected refraction was used as a control. +0.50 DS and +\u0026thinsp;0.75 DS were chosen to include the viewing conditions of Wood et al. [3, 4] Bangerter filters 1.0 and 0.8 were chosen after a pilot study showed that the 0.6 filter and lower were too visually degrading and resulted in an inability to do the test at all. The higher levels of refractive blur used in the previous study [4] were also omitted to reduce the demand on the subjects and because they would reduce visual acuity well below that required in the medical standards. [18]\u003c/p\u003e\n\u003ch3\u003eProcedure\u003c/h3\u003e\n\u003cp\u003eAll procedures were performed at the Colour Vision Clinic of the University of New South Wales. The prevailing COVID-19 hygiene protocols were followed.\u003c/p\u003e\u003cp\u003eVisual acuities were measured without and with Bangerter filters 1.0 and 0.8. Contrast sensitivity was measured binocularly using the MARS test (Mars Perceptrix Corporation, Chappaqua, NY, USA) with best corrected refraction followed by added Bangerter filters.\u003c/p\u003e\u003cp\u003eThe RLLT was administered according to the instruction manual with the participant seated 6 m from the instrument in a normally lit room (300 lux) without significant glare and no visible windows. Ambient lighting has been shown to have no effect on the results of the Farnsworth lantern. [33]\u003c/p\u003e\u003cp\u003eThey were instructed: \u0026ldquo;You will be shown a pair of lights, one above the other for two seconds. I want you to tell me what colours you see. Tell me the top one first. The only colours you will be shown are red, yellow and green and these are the only colour names that you can use. In some cases there is only one light, in which case respond, \u0026ldquo;no light\u0026rdquo;, again in the order of top first, then bottom.\u0026rdquo;\u003c/p\u003e\u003cp\u003eBreaks were given after each test to minimise patient fatigue.\u003c/p\u003e\u003cp\u003e\u0026ldquo;Red-signal related errors\u0026rdquo; were defined as incorrect responses involving the signal red. These included any missed red, red reported as yellow and red reported as green. The outcome for red-signal related errors was the proportion of the total number of red presentations.\u003c/p\u003e"},{"header":"Results","content":"\u003cp\u003eA total of 20 participants completed the study. Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e provides participant demographics Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e provides details of visual acuity in the five states. The subjects all had better than 6/9 visual acuity, the worst being one case of 6/6\u0026thinsp;\u0026minus;\u0026thinsp;1.\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eDemographics of the study participants (mean\u0026thinsp;\u0026plusmn;\u0026thinsp;1 standard deviation).\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"2\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eCharacteristic\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eValue (mean\u0026thinsp;\u0026plusmn;\u0026thinsp;1 s)\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eAge (years)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e22.4\u0026thinsp;\u0026plusmn;\u0026thinsp;1.1\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eGender\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eMale, \u003cem\u003en\u003c/em\u003e (%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e10 (50)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eFemale, \u003cem\u003en\u003c/em\u003e (%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e10 (50)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eVisual acuity of the participants.\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"6\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003eBest corrected\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e\u003cp\u003eBangerter\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e\u003cp\u003eRefractive blur\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003e1\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.8\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.50 D\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.75 D\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eMean\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e-0.11\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e0.05\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.23\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e0.17\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e0.30\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSD\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e0.06\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e0.09\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.14\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e0.08\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e0.10\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003emedian\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e-0.10\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e0.05\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.23\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e0.18\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e0.31\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e1st quartile\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e-0.12\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e-0.02\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.14\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e0.09\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e0.21\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e3rd quartile\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e-0.08\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e0.10\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.30\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e0.23\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e0.38\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSkewness\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e-0.11\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e0.37\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.40\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e0.35\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e0.42\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eAbsolute values of skewness\u0026thinsp;\u0026le;\u0026thinsp;1.0 indicate a normal distribution. [34]\u003c/p\u003e\u003cp\u003eFigure \u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e shows the relationship between number of errors made naming red, LogMAR visual acuity and Bangerter induced blur, as an example. Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e lists the Peason correlation coefficients for each level of blur and the significance of the value. The same analysis has been carried out on the yellow and green errors. There were no significant relationships found between number of errors made and visual acuity within the three induced blur levels of each blur type but there was a significant relationship, p\u0026thinsp;\u0026lt;\u0026thinsp;0.01, for the pooled data between errors made and visual acuity.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eCorrelation coefficients for the relationship between visual acuity and number of red naming errors for each blur type and for the results as a whole\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"5\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e\u003cth align=\"left\" colspan=\"4\" nameend=\"c5\" namest=\"c2\"\u003e\u003cp\u003eRed errors\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eNo blur\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eB 0.8\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eB 0.6\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003eAll\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eCorrelation\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0.327\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0.420\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.107\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.745\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSignificance\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003ep\u0026thinsp;\u0026gt;\u0026thinsp;0.05\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003ep\u0026thinsp;\u0026gt;\u0026thinsp;0.05\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003ep\u0026thinsp;\u0026gt;\u0026thinsp;0.05\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003ep\u0026thinsp;\u0026lt;\u0026thinsp;0.01\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eThis analysis was then carried on both types of blur and for each colour. No significant relationship was found within blur levels and types. For the pooled data, the results are set out in Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab4\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 4\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eCorrelation coefficients and significance for the relationship between number of naming errors and visual acuity for each blur type.\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"4\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e\u003cth align=\"left\" colspan=\"3\" nameend=\"c4\" namest=\"c2\"\u003e\u003cp\u003eErrors per subject\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eBlur type\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eRed\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eYellow\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eGreen\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eBangerter\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0.745\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e-0.074\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.546\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003ep\u0026thinsp;\u0026lt;\u0026thinsp;0.01\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003ens\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003ep\u0026thinsp;\u0026lt;\u0026thinsp;0.01\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eRefractive\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0.288\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e-0.088\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.375\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0.01\u0026thinsp;\u0026lt;\u0026thinsp;p\u0026thinsp;\u0026lt;\u0026thinsp;0.05\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003ens\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003ep\u0026thinsp;\u0026lt;\u0026thinsp;0.01\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eFigure \u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e shows the proportion of errors made on each of the signal colours, these comprise all the errors for each signal colour, that is, signal misnamed or not seen. The responses where the subject reported a colour when none were present are not included. This error occurred only once in the unblurred state, 3 subjects each made 1 error in each of the refractive blur states, there were no errors in the lesser non-refractive blur state and 2 subjects made an error and a subject made 3 errors in the greater non-refractive blur state.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"BlockQuote\"\u003e\u003cp\u003eFigure 4: Relationship between mean LogMAR visual acuity and mean red signal errors for non-refractive (Bangerter filter) and refractive blur. Error bars are \u0026plusmn;\u0026thinsp;1 standard error in proportion of errors and visual acuity. The Y error bars may be smaller than the symbol.\u003c/p\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eFigure 4 shows the breakdown of red signal related errors, that is when a red signal is missed or red miscalled as yellow or green.\u003c/p\u003e\u003cp\u003eErrors occurred far more often with red than yellow or green (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.0001) and with Bangerter filter blur more than refractive blur (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.0001). Failing to see a red signal rather, than misnaming the red as yellow or green, was the most predominant error (p\u0026thinsp;\u0026lt;\u0026thinsp;0.0001) and far more easily induced by Bangerter filter than refractive blur (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.0001) and is a lot less common than miscalling red as yellow (p\u0026thinsp;\u0026lt;\u0026thinsp;0.0001). (Paired t-tests)\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eThe predominant effect of both types of blur is to cause the observers to miss the red signals rather than misname them. While miscalling red as yellow is the second most common error, it is very much less frequent than failing to see the red. The previous studies [3, 4] used both bright and dim backgrounds, with different mis-naming rates. The conditions in the current experiment are probably intermediate between previous conditions. In addition, the second clear effect is that the Bangerter filters, despite causing less loss in visual acuity than refractive blur, give rise to more colour naming errors of all types. This may be seen by comparing the filled and unfilled symbols in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e. Bangerter filters also give rise to more scattered light than ophthalmic lenses (see appendix), so that the less immediate background of the room lit to 250 lx maybe more effective in masking the signals.\u003c/p\u003e\u003cp\u003eThe results show that responses with refractive blur show fewer errors than the bright surrounds of the previous studies, where a significant effect of refractive blur on the miscalling of red as \u0026ldquo;orange-yellow\u0026rdquo; was reported. While the authors wrote about red looking yellow, the actual experiments did not permit the use \u0026ldquo;yellow\u0026rdquo; alone as a descriptor. The classical studies of colour naming have shown theoretically [35] and in practice [36] that, given the choice of colour names of red, orange and yellow, wavelengths longer than about 605 nm were never called \u0026ldquo;yellow\u0026rdquo; and shorter than 605 nm were never called \u0026ldquo;red\u0026rdquo;. The introduction of the option of \u0026ldquo;orange\u0026rdquo; creates considerable overlap, such that around 620 nm is called \u0026rdquo;red\u0026rdquo; and \u0026ldquo;orange\u0026rdquo; approximately equally frequently and around 570 nm called \u0026ldquo;yellow\u0026rdquo; and \u0026ldquo;orange\u0026rdquo; equally frequently. The distinction is less clear for \u0026ldquo;low intensity\u0026rdquo; stimuli. [36] Holmes [9] collected but did not report data on orange. He reports that \u0026ldquo;Experiments in the differentiation between yellow and orange showed considerable confusion between these colour names at low illuminations\u0026rdquo;. Soon \u0026amp; Cole [37] did not use the response \u0026ldquo;orange\u0026rdquo; either. In addition, their Red 2 and Red 3, see their Table II, are too orange (y\u0026thinsp;\u0026gt;\u0026thinsp;0.292) to comply with the prevailing requirements [8] for wayside signals although they do comply with the requirements for highway/rail crossing (being the same as for traffic signals generally [38, 39]). Red 1 was never called \u0026ldquo;yellow\u0026rdquo; by young or old subjects. Similarly, Yellow 2 and Yellow 3 are too green to comply (y\u0026thinsp;\u0026gt;\u0026thinsp;0.430). So there is blurred borderline between red and orange and between yellow and orange that does not exist between yellow and red.\u003c/p\u003e\u003cp\u003eIn the earlier studies, [4] the option to report a signal as not seen was not provided, although in the earlier of the two studies, this was reported as a response but not analysed. The problem here is that, if a signal is not seen, then the subject will be required to guess and will choose a response at random. So, half the time a failure to see a signal will result in a two alternative forced-choice response of the wrong colour. Thus, mis-calling of red as \u0026ldquo;orange-yellow\u0026rdquo; would have occurred 50% of the time that the signal was not seen. Since the yellow has about twice the luminous intensity of the red in their experiments, not seeing the yellow will occur significantly less often. In the current study, participants were given options between \u0026ldquo;red\u0026rdquo;, \u0026ldquo;yellow\u0026rdquo;, \u0026ldquo;green\u0026rdquo; or \u0026ldquo;no light\u0026rdquo;. This is reflective of signalling practices and represents the task that train drivers are given and reds that are not seen will not be called \u0026ldquo;yellow-orange\u0026rdquo;.\u003c/p\u003e\u003cp\u003eA second reason as to why reds were less likely to be miscalled as yellow in this study, if the effects are related to chromatic aberration, could be due to the narrower band spectral distributions of the LED lights in the RLLT. The narrower spectral bandwidth of LEDs compared with incandescent signals with a broad band filter is well illustrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e of the earlier previous study as is the narrower spectral distribution of the interference filter. [3] The authors do not separate the responses for the broad band and narrow band red other than qualitative comments on than anomalous results of three observers. It may also be seen in the traffic signals used in the ISO test method standard for eye and face protection, [40] see Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e5\u003c/span\u003e. These data were collected in the Optics \u0026amp; Radiometry Laboratory, UNSW (ORLAB). Thus any chromatic aberration effects [41, 42] may be different for the two types of signal.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eThe phenomenon was originally described [3] as occurring when signals were blurred because they were viewed through the intermediate corridor of a progressive lens, although it was noted that blur in general also gave rise to the observation. The authors discounted \u0026ldquo;chromatic aberration\u0026rdquo; as an explanation because it was in the wrong direction to explain the results since red is focussed, in the refractively blurred condition, closer to the retina not further away. This argument assumes focus is accurate without any leads of accommodation as would occur for example in darker environments in a phenomenon known as empty field myopia. [43] Wood et al\u0026rsquo;s argument implicitly addressed longitudinal chromatic aberration but they were not specific. [3]\u003c/p\u003e\u003cp\u003eAs an anecdotal comment, some years ago a request for resolution of a complaint came to the ORLAB which is the only testing laboratory in Australia that is ISO/IEC 17025 [32] accredited to test to the eye and face protection standards. The complaint related to two prescription eye protectors that were supposed to be identical but the newer pair caused the wearer to see coloured fringes and the older pair did not. Both pairs were the same material (polycarbonate), the same design of progressive lens, the same distance prescription and near addition, the same frame, the same base curves and the same centration distances. What was identified as the only difference was that the newer pair had prism thinning applied in manufacture. This is a process in which equal vertical prisms are worked on the two lenses to reduce the thickness and make the lenses lighter and minimise edge thickness around the superior edge. Polycarbonate is widely used in eye protection being the most impact resistant of the lens materials. [44] Complaints about coloured fringes, especially associated with higher refractive powers, are, anecdotally, relatively common with polycarbonate given that it has the lowest Abbe number of all the ophthalmic lenses (30 compared with 58 for hard resin, allyl glycol carbonate). As a consequence, the phenomenon originally described by Wood et al [3] may be related to lateral chromatic aberration from the prism and the blur effect may be coincidental.\u003c/p\u003e\u003cp\u003eThe actual colours and luminous intensities of the RLLT stimuli are considered commercial in confidence but they were chosen to comply with CIE S 004. [45] See Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e6\u003c/span\u003e. The CIE limits are a little more liberal in the green direction than the ARTC limits [7] but the colours used in the previous study [4] would comply. However, also shown are the yellow limits for traffic signals in Australia. [38] These may be seen to be much more restrictive in the red direction compared with both the CIE and ARTC. So the subject group will comprise people who are familiar with the less orange road traffic signals, which may influence their use of the term \u0026ldquo;orange-yellow\u0026rdquo;.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eThe luminous intensities of the stimuli in the RLLT were deliberately varied to reflect the real-life situations where the viewing distances may vary and the observer may not be in the direction of the maximum intensity. While the actual specifications of the signals are considered commercial in confidence, they were derived after making measurements on all the models of signal made available by Railcorp NSW at the time. It is fair to say that they will on average, be significantly lower than the stimuli in the Wood et al study. [4]\u003c/p\u003e\u003cp\u003eThe use of Bangerter filters was implemented in this study to investigate whether longitudinal chromatic aberrations are involved in the colour misperception effect. Bangerter filters do not refract light but behave more like a Gaussian filter thus longitudinal chromatic aberrations cannot be induced. A study by Gupta et al [41] demonstrated that longitudinal chromatic aberrations and not monochromatic aberrations may be linked with the colour misperception phenomenon. This effect is also not affected by L/M cone ratio. They also proposed that an additional defocus dependent neural mechanism may also contribute to change in colour appearance. [45] Hence, the presence of missed reds and reds called yellow are indicative that factors other than longitudinal chromatic aberration may be inducing a colour misperception effect. The presence of red misperceptions with the Bangerter filters in this study raises the question as to whether a non-optical defocus mechanism is involved.\u003c/p\u003e\u003cp\u003eThe errors made by participants under best corrected conditions are anomalous in that 2 participants (10%) failed the RLLT. In the development study, [13] 106 colour vision \u0026ldquo;normals\u0026rdquo;; only one (0.9%) individual failed. At the time, a pass on the RLLT constituted less \u0026le;\u0026thinsp;two misnamings, \u0026le; one green or yellow missed and \u0026le;\u0026thinsp;one blank named as a colour. In the commercially available version and based on a decision by RailCorp NSW (now incorporated into Transport for NSW), any missed or miscalled reds constitute a fail. However, in an experimental domain, naive participants may not invest sufficiently to avoid making judgement errors. This is known as the mutable-zero effect in risky choices. [46]\u003c/p\u003e\u003cp\u003eThere are probably many factors leading to the occurrence of a SPAD. These could be due to a signal being missed, being misperceived or some other factor. There does not seem to have been any consideration of this issue in any of the studies of causes of SPADs. In the case of the NSW railways, the investigation of SPADs does not include direct questions about whether the signal was not seen or seen as yellow (Casolin, A. personal communication) and there are no reports from other jurisdictions to be found. As a consequence, the hypothesised [4] association between SPADs must be seen as very tentative at this stage.\u003c/p\u003e\u003cp\u003eAt the time of the first Wood et al study [3], the manufacturing standard on prescription eye protection, AS/NZS 1337.6 [47] was yet to be published and the conventional wisdom was that polycarbonate was the material of choice for medium impact occupational eye protection. \u0026ldquo;Medium impact\u0026rdquo; in AS/NZS 1337 was the same, at the time of Wood et al [3] as \u0026ldquo;low energy impact\u0026rdquo; in EN 166:2001 [48] and \u0026ldquo;high velocity impact\u0026rdquo; for spectacle type eye protectors in ANSI Z87.1:2003 [49]. Since that time, other lens materials for this level of impact protection have come in to use. While polycarbonate remains the most impact resistant material, [50] there are other materials (most notably polyurethane, introduced in 2001) that do comply with the medium impact requirements, have a lower refractive index and a higher Abbe number than polycarbonate. So, if the coloured fringing is an issue, there is, these days, an alternative solution.\u003c/p\u003e"},{"header":"Conclusions","content":"\u003cp\u003eRather than a colour misperception, the errors seem to be more related to simply missing the signal. This current study does find that low refractive blur and non-refractive blur does cause red, more than yellow or green, to be missed rather than misnamed. This study also shows that non\u0026ndash;refractive blur is a more potent means of inducing error in colour detection and, to a lesser extent, recognition in a simulated practical test.\u003c/p\u003e\u003cp\u003eThere are several methodological reasons why this study gives different results from the earlier studies [3] given the difference in the stimuli and, especially, in the responses required of the experimental subjects. It was been suggested that stray light and the Abney effect could [3, 4] play a role in the misnaming since the desaturation of red leads to an increased likelihood of naming as yellow. Thus the bright surround was associated with the error which did not occur. Adaptation is also affected and affects colour naming is a complex way. [51] The test conditions in this study would lead to an adaptation level that is intermediate between the bright and dark surround of the previous study.. In addition, Bangerter filters have been shown to be \u0026ldquo;qualitatively different\u0026rdquo; from defocus blur and \u0026ldquo;do not exhibit spurious resolution and phase shifts, as does defocus\u0026rdquo; with grayscale stimuli. [52]\u003c/p\u003e\u003cp\u003eGiven that the RLLT is a simulated practical test, the results of this study suggest that the conclusions of the original observations [3, 4] of miscalling red as \u0026ldquo;yellow\u0026rdquo; having practical consequences may be overstated. Until the post-SPAD de-briefing questions include the differentiation of \u0026ldquo;red signal not seen\u0026rdquo; and \u0026ldquo;red signal not perceived as red\u0026rdquo; the link is unlikely to be resolved. Even though the Goodwell OK collision [53] involved a SPAD and the vision and colour vision of the engineer were identified as inadequate, the incident involved failing to reduce speed to 40 mph in response to a flashing yellow, failing to reduce speed further to 30 mph in response the yellow over red signals and, finally, failing to stop, or even slow down, at a red signal. Even misperceiving the red as yellow should have led to a slowing of the train. So this collision was preceded by failing to see red and yellow signals with the number of lights being redundant information that should have resulted in a response even if the colour was misperceived.\u003c/p\u003e\u003cp\u003eSince the medical standards [18] also include a requirement for visual acuity (6/9 in the better eye), this may be an indirect way of minimising this issue in practice.\u003c/p\u003e\u003cp\u003eThe extent to which the results, from a young population, may be extrapolated to older observers is not known but Soon and Cole [37] showed no age effect in the recognition of Red 1 (the only rail use compliant red).\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003eDisclosure Statement\u003c/p\u003e\n\u003cp\u003eThe authors report there are no competing interests to declare.\u003c/p\u003e\u003ch2\u003edata availablity\u003c/h2\u003e\u003cp\u003eThe data that support the findings of this study are available from the corresponding author, [SJD], upon reasonable request.\u003c/p\u003e\u003c/p\u003e\u003ch2\u003eFunding statement\u003c/h2\u003e\u003cp\u003eThis project did not receive any funding.\u003c/p\u003e\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eJC and TN carried out the data collection, literature search, initial data analysis and first draft of project report. They assisted in the ethics application.MB assisted with method design and ethics application, oversaw the data collection, provided the major revision of the first data analysis and reviewed drafts of the paper and responses to reviewers. VH assisted with method design and ethics application, oversaw the data collection and reviewed drafts of the paper and responses to reviewers. .SD provided the concept of the project, first draft of the method, ethics application, oversight of the data collection, further data analysis, drafting of the report into the paper and preparation of the revisions and responses to reviewers\u003c/p\u003e\u003ch2\u003eAcknowledgement\u003c/h2\u003e\u003cp\u003eTo Dr Armand Casolin, Chief Health Officer, Safety, Environment \u0026amp; Regulation, Transport for NSW for his advice. To the staff of ORLAB, UNSW for the use of the instruments and assistance with the spectral transmittance and haze measurements. To the reviewers (especially reviewer 1) who helped make it a better paper.\u003c/p\u003e\u003ch2\u003eData Availability\u003c/h2\u003e\u003cp\u003eThe data that support the findings of this study are available from the corresponding author, [SJD], upon reasonable request.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eNikandros G, Tombs D. Measuring Railway Signals Passed At Danger. In: Cant T, editor. 12th Australian Conference on Safety Critical Systems and Software. Adelaide: Conferences in Research and Practice in Information Technology (CRPIT); 2007. p. 41-6. http://www.ntsb.gov/investigations/AccidentReports/Reports/RAR1302.pdf\u003c/li\u003e\n\u003cli\u003eRail Safety and Standards Board. Annual Safety Performance Report 2012/13. London.: Rail Safety and Standards Board; 2013. https://www.worldtransitresearch.info/research/4859/\u003c/li\u003e\n\u003cli\u003eWood JM, Atchison DA, Chaparro A. When Red Lights Look Yellow. Invest Ophth Vis Sci. 2005;46 (11):4348-52. https://doi.org/10.1167/iovs.04-1513.\u003c/li\u003e\n\u003cli\u003eWood JM, Atchison DA, Black AA, G.S. L. Low levels of refractive blur increase the risk of colour misperception of red train signals. Ophthalmic Physiol Opt. 2022;42:872-8. https://doi.org/10.1111/opo.12979.\u003c/li\u003e\n\u003cli\u003eNaweed A, Trigg J, Cloete S, Allan P, Bentley T. Throwing good money after SPAD? Exploring the cost of signal passed at danger (SPAD) incidents to Australasian rail organisations. Saf Sci. 2018;109:157-64. https://doi.org/10.1016/j.ssci.2018.05.018.\u003c/li\u003e\n\u003cli\u003evan der Flier H, Schoonman W. Railway signals passed at danger: Situational and personal factors underlying stop signal abuse. Appl Ergon. 1988;19(2):135-41. https://doi.org/10.1016/0003-6870(88)90006-3.\u003c/li\u003e\n\u003cli\u003eARTC. Light Signals. SPS 11 - (RIC Standard: SC07 1000 00SP). Australian Rail Track Corporation Limited; 2005.\u003c/li\u003e\n\u003cli\u003eARTC. ESA-04-01 Colourlight signals and indicators. Australian Rail Track Corporation Limited; 2024. http://extranet.artc.com.au/docs/eng/signal/procedures/material/ESA-04-01.pdf \u003c/li\u003e\n\u003cli\u003eHolmes JG. Colour recognition of very small light sources. Docum Ophthalmol. 1949;3(1):240-50. https://doi.org/10.1007/BF00162605.\u003c/li\u003e\n\u003cli\u003eTopley H. Sight testing for the merchant navy. 16:36-47. B J Physiol Opt. 1959;16:36-47. \u003c/li\u003e\n\u003cli\u003eCole BL, Vingrys AJ. Who fails lantern tests?. Doc Ophthalmol. 1983;55 (3):9. https://doi.org/10.1007/BF00140807.\u003c/li\u003e\n\u003cli\u003eInternational Maritime Organisation. Conventions on the International Regulations for Preventing Collisions at Sea. (COLREGs). London: International Maritime Organisation; 1972. https://www.imorules.com/COLREG90_RULES.html\u003c/li\u003e\n\u003cli\u003eDain SJ, Casolin A, Long J, Hilmi MR. Color vision and the railways: Part 1 The Railway LED Lantern Test. Optom Vis Sci. 2015;92(2):138-46. https://doi.org/10.1097/OPX.0000000000000460.\u003c/li\u003e\n\u003cli\u003eVingrys AJ, Cole BL. Validation of the Holmes-Wright lanterns for testing colour vision. Ophthal Physiol Opt. 1986;3 (2):16. https://doi.org/10.1111/j.1475-1313.1983.tb00593.x.\u003c/li\u003e\n\u003cli\u003eFarnsworth D, Foreman P. Development and trial of New London Navy Lantern as a selection test for serviceable color vision. Groton, CT, USA: Naval Submarine Medical Research Laboratory; 1946. \u003c/li\u003e\n\u003cli\u003eDain SJ, Casolin A, Long J. Color vision and the railways: Part 2. Comparison of the CN Lantern used on the Canadian Railways and Railway LED lantern tests. Optom Vis Sci. 2015;92(2):147-51. https://doi.org/10.1097/OPX.0000000000000461.\u003c/li\u003e\n\u003cli\u003eDain SJ, Casolin A, Long J. Color Vision and the Railways: Part 3. Comparison of FaLant, OPTEC 900, and Railway LED Lantern Tests. Optom Vis Sci. 2015;92(2):152-6. https://doi.org/10.1097/OPX.0000000000000462.\u003c/li\u003e\n\u003cli\u003eNational Transport Commission. National Standard for Health Assessment of Rail Safety Workers. Melbourne: National Transport Commission; 2024. https://www.ntc.gov.au/sites/default/files/assets/files/Rail%20Standard%202024.pdf \u003c/li\u003e\n\u003cli\u003eCole BL, Vingrys AJ. A survey and evaluation of lantern tests of color vision. Am J Optom Physiol Opt. 1982;59 (4):9. https://doi.org/https://journals.lww.com/optvissci/abstract/1982/04000/A_Survey_and_Evaluation_of_Lantern_Tests_of_Color.9.aspx.\u003c/li\u003e\n\u003cli\u003eHovis JK, Oliphant D. A lantern color vision test for the rail industry. Am J Indust Med. 2000;38 (6):681-7. https://doi.org/10.1002/1097-0274(200012)38:6\u0026lt;681::AID-AJIM8\u0026gt;3.0.CO;2-4.\u003c/li\u003e\n\u003cli\u003eNeubert FR. Colour vision in the consulting room. Br J Ophthalmol. 1947;31:275-88. https://doi.org/10.1136/bjo.31.5.275.\u003c/li\u003e\n\u003cli\u003eOdell NV, Leske DA, Hatt SR, Adams WE, Holmes JM. The effect of Bangerter filters on optotype acuity, Vernier acuity, and contrast sensitivity. J AAPOS. 2008;12:555-5590. https://doi.org/10.1016/j.jaapos.2008.04.012.\u003c/li\u003e\n\u003cli\u003eDain SJ, Hovis JK, Hoskin AK. The specification of color limits in eye protection lenses for use when color-contingent clinical observations are made. Color Res Appl. 2022;47:1118-33. https://doi.org/10.1002/col.22795.\u003c/li\u003e\n\u003cli\u003eAS 16321-4 (Int) Eye and face protection for occupational use Protection against biological hazards. Sydney: Standards Australia; 2023.\u003c/li\u003e\n\u003cli\u003eISO 12609-1 Eye and face protection against intense light sources used on humans and animals for cosmetic and medical applications Part 1: Specification for products. Geneva: International Organization for Standardization; 2021.\u003c/li\u003e\n\u003cli\u003eISO 12312-1 Eye and Face protection\u0026mdash; Sunglasses and related eyewear - Part 1: Sunglasses for general use. Geneva: International Organization for Standardization; 2022.\u003c/li\u003e\n\u003cli\u003eBaldasso M, Roy M, Boon MY, Dain SJ. Effect of blue\u0026ndash;blocking lenses on colour discrimination. Clin Exp Optom. 2021;104(1):56-61. https://doi.org/10.1111/cxo.13139.\u003c/li\u003e\n\u003cli\u003eNational Research Council. Procedures for Color Vision Testing. Report of the Working Group 41. Washington, DC: Committee on Vision. Assembly of Behavioral and Social Sciences. National Research Council. National Academy Press; 1981. https://pubmed.ncbi.nlm.nih.gov/25032450/\u003c/li\u003e\n\u003cli\u003eDain SJ, Atchison DA, Hovis JK, Boon M-Y. Lighting for color vision examination in the era of LEDs: the FM100Hue Test. J Opt Soc Am A. 2020;37(4):A122-A32. https://doi.org/10.1364/JOSAA.382301.\u003c/li\u003e\n\u003cli\u003eDain SJ, Hovis JK. Recommendations and requirements for the wavelengths in Rayleigh equation anomaloscopes. J Opt Soc Am A. 2023;40(3):A121-A9. https://doi.org/10.1364/JOSAA.477144.\u003c/li\u003e\n\u003cli\u003eISO 5868 Ophthalmic optics and instruments \u0026mdash; Anomaloscopes for the diagnosis of red-green colour vision deficiencies. Geneva: International Organization for Standardization; 2025.\u003c/li\u003e\n\u003cli\u003eISO/IEC 17025 General requirements for the competence of testing and calibration laboratories. Geneva: International Organization for Standardization and International Electrotechnical Commission; 2019.\u003c/li\u003e\n\u003cli\u003eDain SJ, Honson V, Ang J. The effect of two lighting conditions on performance of the Farnsworth Lantern color vision test. Aviat Space Environ Med 1988;59 (4):3. https://doi.org/https://asma.kglmeridian.com/downloadpdf/view/journals/asem/59/4/article-p371.pdf.\u003c/li\u003e\n\u003cli\u003eMishra P, Pandey CM, Singh U, Gupta A, Sahu C, Keshri A. Descriptive Statistics and Normality Tests for Statistical Data. Ann Card Anaesth. 2016;22:67-72. https://doi.org/10.4103/aca.ACA_157_18.\u003c/li\u003e\n\u003cli\u003eGraham CH. Sensation and perception in an objective psychology. Psych Rev. 1958;65(2):65-76. https://doi.org/10.1037/h0046960.\u003c/li\u003e\n\u003cli\u003eBeare AC. Color-name as a function of wavelength. Am J Psychol. 1963;76(2):248-56. https://doi.org/https://www.jstor.org/stable/1419161.\u003c/li\u003e\n\u003cli\u003eSoon FC, Cole BL. Did the CIE get it right? A critical test of the CIE color domains for signal lights. Color Res Appl. 2001;26(2):109-22. https://doi.org/10.1002/1520-6378(200104)26:2%3C109::AID-COL1002%3E3.0.CO;2-Z.\u003c/li\u003e\n\u003cli\u003eAS 2144 Traffic Signal lanterns. Sydney: Standards Australia; 2023.\u003c/li\u003e\n\u003cli\u003eISO 16508 (CIE S 006.1:1998) Road Traffic Lights \u0026mdash; Photometric Properties of 200 mm Roundel Signals. Geneva: International Organization for Standardization; 1999.\u003c/li\u003e\n\u003cli\u003eISO 18526-2 Eye and face protection \u0026ndash; Test methods \u0026ndash; Part 2: Physical optical properties. Geneva: International Organization for Standardization; 2020.\u003c/li\u003e\n\u003cli\u003eGupta P, Atchison DA, Zele AJ, Guo H. The effect of optical aberrations on the colour appearance of small lights. J Vis. 2008;8(17):43. https://doi.org/10.1167/8.17.43.\u003c/li\u003e\n\u003cli\u003eGupta P, Guo H, Atchison DA, Zele AJ. Effect of optical aberrations on the color appearance of small defocused lights. J Opt Soc Am A 2010;27(5):960-7. https://doi.org/10.1364/JOSAA.27.000960.\u003c/li\u003e\n\u003cli\u003eWestheimer G. Accommodation measurements in empty visual fields. J Opt Soc Am. 1957;47(8):714-8. https://doi.org/10.1364/JOSA.47.000714.\u003c/li\u003e\n\u003cli\u003eDain SJ. Materials for occupational eye protectors. Clin Exp Optom. 2012;95 (2):129-39. https://doi.org/10.1111/j.1444-0938.2012.00704.x.\u003c/li\u003e\n\u003cli\u003eCIE S 004 Colours of light signals. Vienna: Commission Internationale de l\u0026rsquo;\u0026Eacute;clairage; 2001.\u003c/li\u003e\n\u003cli\u003eScholten M, Read D, Stewart N. The framing of nothing and the psychology of choice. J Risk Uncertain. 2019;59:125-49. https://doi.org/10.1007/s11166-019-09313-5.\u003c/li\u003e\n\u003cli\u003eAS/NZS 1337.6 Personal eye protection Part 6: Prescription eye protectors against low and medium impact. Sydney: Standards Australia/Standards New Zealand; 2007.\u003c/li\u003e\n\u003cli\u003eCEN. EN 166 Personal eye-protection - Specifications. Brussels: Comit\u0026eacute; Europ\u0026eacute;en de Normalisation (CEN); 2001.\u003c/li\u003e\n\u003cli\u003eASSP/ANSI Z87.1 American National Standard for Occupational and Educational Personal Eye and Face Protection Devices. Park Ridge, IL: American Society of Safety Professionals; 2003.\u003c/li\u003e\n\u003cli\u003eChou BR, Yuen GS, Dain SJ. Ballistic impact resistance of selected organic ophthalmic lenses. Clin Exp Optom. 2011;94 (6):568-74. https://doi.org/10.1111/j.1444-0938.2011.00651.x.\u003c/li\u003e\n\u003cli\u003eWebster MA. Human colour perception and its adaptation. Netw: Comput Neural Syst. 1996;7(4):587-634. https://doi.org/10.1088/0954-898X_7_4_002.\u003c/li\u003e\n\u003cli\u003eP\u0026eacute;rez, GM, Archer SM, Artal P. Optical Characterization of Bangerter Foils. Invest Ophthalmol Vis Sci. 2010;51:609-613. https://doi.org/10.1167/iovs.09-3726.\u003c/li\u003e\n\u003cli\u003eNational Transportation Safety Board. Head-On Collision of Two Union Pacific Railroad Freight Trains Near Goodwell, Oklahoma June 24, 2012. NTSB/RAR-13/02 PB2013-107679. Washington, DC.: National Transportation Safety Board; 2013. http://www.ntsb.gov/investigations/AccidentReports/Reports/RAR1302.pdf \u003c/li\u003e\n\u003cli\u003eAS 16321.4. (INT) Eye and face protection for occupational use Part 4: Protection against biological hazards. Sydney: Standards Australia; 2023.\u003c/li\u003e\n\u003cli\u003eISO 14782 Plastics - Determination of haze for transparent materials. Geneva: International Organization for Standardization; 2021.\u003c/li\u003e\n\u003cli\u003eASTM International. D1003-11 Standard Test Method for Haze and Luminous Transmittance of Transparent Plastics. West Conshohocken, PA: ASTM International; 2011.\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"ophthalmic-and-physiological-optics","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"","sideBox":"Learn more about [Ophthalmic and Physiological Optics](https://link.springer.com/journal/44402)","snPcode":"44402","submissionUrl":"https://submission.springernature.com/new-submission/44402/3?","title":"Ophthalmic and Physiological Optics","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Springer Open","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"colour vision, railway signals, occupational safety, vision standards, blur","lastPublishedDoi":"10.21203/rs.3.rs-8052714/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8052714/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003ePurpose: Previous research has reported a significant effect of refractive defocus on correct identification of red signals. The purpose of this study is to investigate the effects of both refractive defocus and non-refractive defocus (using Bangerter filters) on the perception of rail signals using the Railway LED Lantern Test (RLLT). The RLLT is the simulated practical test nominated in the Australian National Standard for Health Assessment of Railway Safety Workers.\u003c/p\u003e\n\u003cp\u003eMethod: Participants were 19-59 years old, best corrected visual acuity (BVCA) was required to be no worse than 6/9 binocularly. Subjects with current or active ocular conditions were excluded and sufficiency in English was required. Best corrected refraction, visual acuity and colour vision was assessed. Participants carried out the RLLT binocularly under five conditions: best corrected, +0.50DS, +0.75DS and Bangerter filters 1.0 and 0.8\u003c/p\u003e\n\u003cp\u003eResults: 10 male and 10 female subjects completed the study; age range 20 to 25 and mean age 22.4 ± 1.1 years. BVCA was 6/6 (logMAR 0.0 or better.\u003c/p\u003e\n\u003cp\u003eErrors occurred far more often with red than yellow or green (\u003cem\u003ep\u003c/em\u003e \u0026lt;0.0001) and with Bangerter filter blur more than refractive blur (\u003cem\u003ep\u003c/em\u003e \u0026lt;0.0001). Failing to see a red signal rather, than misnaming the red as yellow or green, was the predominant error (p \u0026lt;0.0001) and induced far more frequently by Bangerter filters than refractive blur (\u003cem\u003ep\u003c/em\u003e \u0026lt;0.0001). This error was far more common than miscalling red as yellow (p \u0026lt;0.0001). (Paired t-tests)\u003c/p\u003e\n\u003cp\u003eConclusion: These findings suggest that a large proportion of errors are due to not seeing the red signal rather than miscalling the red as yellow or green. Non-refractive blur was found to cause a greater increase in colour errors.\u003c/p\u003e","manuscriptTitle":"LED railway signal detection rather than recognition is affected by both refractive and non-refractive blur","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-11-24 16:40:08","doi":"10.21203/rs.3.rs-8052714/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2025-12-01T21:21:03+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-12-01T20:24:02+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"53628298431324722625511497768225409583","date":"2025-11-14T15:49:02+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-11-12T17:13:41+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"27785772225578175050117264128808429673","date":"2025-11-12T15:53:28+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-11-12T15:43:22+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-11-12T15:38:00+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-11-12T13:48:33+00:00","index":"","fulltext":""},{"type":"submitted","content":"Ophthalmic and Physiological Optics","date":"2025-11-07T03:45:20+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"ophthalmic-and-physiological-optics","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"","sideBox":"Learn more about [Ophthalmic and Physiological Optics](https://link.springer.com/journal/44402)","snPcode":"44402","submissionUrl":"https://submission.springernature.com/new-submission/44402/3?","title":"Ophthalmic and Physiological Optics","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Springer Open","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"8bf75800-b3b8-44b4-9c46-21e7fb68b6c5","owner":[],"postedDate":"November 24th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2026-01-12T14:39:07+00:00","versionOfRecord":[],"versionCreatedAt":"2025-11-24 16:40:08","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8052714","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8052714","identity":"rs-8052714","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}