Assessing Urgent Medical Accessibility in Monocentric Megacities: A Bayesian-Optimized GP2SFCA Study of Chengdu

Assessing Urgent Medical Accessibility in Monocentric Megacities: A Bayesian-Optimized GP2SFCA Study of Chengdu | 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 Article Assessing Urgent Medical Accessibility in Monocentric Megacities: A Bayesian-Optimized GP2SFCA Study of Chengdu Chen Luo, Chunyang Liu, Tianshun Ma, Xinrong Hu, Haoyuan Li, Xutong Wang This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8171704/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 26 Mar, 2026 Read the published version in Scientific Reports → Version 1 posted 14 You are reading this latest preprint version Abstract Evaluating urban residents'access to emergency medical care by car is crucial for optimizing public health resources in megacities. To address the challenges of subjective parameter settings and the integration of behavioral preferences with real-time traffic data, this study introduces an integrated analytical framework that combines "behavioral selection, real-time traffic, and parameter optimization." Expanding on the traditional Two-Step Floating Catchment Area (2SFCA) method, this framework incorporates multi-period and multi-threshold real-time travel data. It develops a multi-constraint optimization model that includes spatial equity, Bayesian priors, and operational logic to objectively calibrate the distance decay coefficient (λ), treating it as a variable to be solved rather than preset. The model assesses Chengdu residents' access to Grade-A Tier-3 hospitals during emergencies, simulating hospital choice as a probability-based decision informed by predicted travel times. The analysis uncovers a complex spatiotemporal structure that surpasses a simple core-periphery division. At the macro level, a three-tier zonal differentiation is evident, while at the micro level, a patchy heterogeneity is influenced by fine-grained road networks and polarized medical resources, particularly under 5-minute thresholds. The study also highlights a systematic “dual vulnerability”: regular weekday vulnerability caused by tidal traffic flows, and complex weekend vulnerability due to a spatiotemporal displacement effect from leisure travel, which unexpectedly decreases accessibility even in central urban areas. These patterns reveal deeper structural issues of medical resource “functional lock-in” and “configuration rigidity” within a monocentric city model. Parameter calibration reveals consistent patterns across scenarios: λ increases with shorter emergency time thresholds and during peak hours, mathematically supporting the hypothesis that time pressure heightens sensitivity to distance. This finding, along with the model's robustness confirmed by extensive sensitivity analysis (93.1% of scenarios show minimal fluctuation), ensures that the results are reliable and not artifacts of parameter subjectivity. Theoretically, this research extends the 2SFCA method to dynamic urban settings and offers empirical insight into how human spatial behavior interacts with real-time traffic. Practically, the proposed Gaussian Probability Two-Step Floating Catchment Area (GP2SFCA) model and framework support the optimization of Chengdu’s emergency “life channels” and medical resource allocation, providing a reusable toolkit for similar monocentric megacities. Physical sciences/Engineering Earth and environmental sciences/Environmental social sciences Physical sciences/Mathematics and computing Urgent Driving-based Medical Accessibility Power-law based Probabilistic Choice Model Multi-constraint Bayesian Optimization Spatiotemporal Heterogeneity Parameter Sensitivity Analysis Full Text Additional Declarations No competing interests reported. Cite Share Download PDF Status: Published Journal Publication published 26 Mar, 2026 Read the published version in Scientific Reports → Version 1 posted Editorial decision: Revision requested 01 Feb, 2026 Reviews received at journal 01 Feb, 2026 Reviews received at journal 31 Jan, 2026 Reviews received at journal 26 Jan, 2026 Reviews received at journal 20 Jan, 2026 Reviewers agreed at journal 14 Jan, 2026 Reviewers agreed at journal 13 Jan, 2026 Reviewers agreed at journal 12 Jan, 2026 Reviewers agreed at journal 12 Jan, 2026 Reviewers invited by journal 12 Jan, 2026 Editor invited by journal 26 Nov, 2025 Editor assigned by journal 23 Nov, 2025 Submission checks completed at journal 23 Nov, 2025 First submitted to journal 21 Nov, 2025 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-8171704","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":573943598,"identity":"6794b9ff-cc86-4968-a4af-84982cf236da","order_by":0,"name":"Chen 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Chengdu","fulltext":[],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":false,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":true,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":true,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"scientific-reports","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"scirep","sideBox":"Learn more about [Scientific Reports](http://www.nature.com/srep/)","snPcode":"","submissionUrl":"","title":"Scientific Reports","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Scientific Reports","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"Urgent Driving-based Medical Accessibility, Power-law based Probabilistic Choice Model, Multi-constraint Bayesian Optimization, Spatiotemporal Heterogeneity, Parameter Sensitivity Analysis","lastPublishedDoi":"10.21203/rs.3.rs-8171704/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8171704/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eEvaluating urban residents'access to emergency medical care by car is crucial for optimizing public health resources in megacities. To address the challenges of subjective parameter settings and the integration of behavioral preferences with real-time traffic data, this study introduces an integrated analytical framework that combines \"behavioral selection, real-time traffic, and parameter optimization.\" Expanding on the traditional Two-Step Floating Catchment Area (2SFCA) method, this framework incorporates multi-period and multi-threshold real-time travel data. It develops a multi-constraint optimization model that includes spatial equity, Bayesian priors, and operational logic to objectively calibrate the distance decay coefficient (λ), treating it as a variable to be solved rather than preset. The model assesses Chengdu residents' access to Grade-A Tier-3 hospitals during emergencies, simulating hospital choice as a probability-based decision informed by predicted travel times.\u003c/p\u003e \u003cp\u003eThe analysis uncovers a complex spatiotemporal structure that surpasses a simple core-periphery division. At the macro level, a three-tier zonal differentiation is evident, while at the micro level, a patchy heterogeneity is influenced by fine-grained road networks and polarized medical resources, particularly under 5-minute thresholds. The study also highlights a systematic \u0026ldquo;dual vulnerability\u0026rdquo;: regular weekday vulnerability caused by tidal traffic flows, and complex weekend vulnerability due to a spatiotemporal displacement effect from leisure travel, which unexpectedly decreases accessibility even in central urban areas. These patterns reveal deeper structural issues of medical resource \u0026ldquo;functional lock-in\u0026rdquo; and \u0026ldquo;configuration rigidity\u0026rdquo; within a monocentric city model.\u003c/p\u003e \u003cp\u003eParameter calibration reveals consistent patterns across scenarios: λ increases with shorter emergency time thresholds and during peak hours, mathematically supporting the hypothesis that time pressure heightens sensitivity to distance. This finding, along with the model's robustness confirmed by extensive sensitivity analysis (93.1% of scenarios show minimal fluctuation), ensures that the results are reliable and not artifacts of parameter subjectivity. Theoretically, this research extends the 2SFCA method to dynamic urban settings and offers empirical insight into how human spatial behavior interacts with real-time traffic. Practically, the proposed Gaussian Probability Two-Step Floating Catchment Area (GP2SFCA) model and framework support the optimization of Chengdu\u0026rsquo;s emergency \u0026ldquo;life channels\u0026rdquo; and medical resource allocation, providing a reusable toolkit for similar monocentric megacities.\u003c/p\u003e","manuscriptTitle":"Assessing Urgent Medical Accessibility in Monocentric Megacities: A Bayesian-Optimized GP2SFCA Study of Chengdu","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-01-14 12:10:24","doi":"10.21203/rs.3.rs-8171704/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2026-02-02T04:56:17+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-02-01T16:52:04+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-01-31T11:44:52+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-01-26T05:42:49+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-01-20T05:58:07+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"142010059851751556698441621205417182770","date":"2026-01-14T09:41:58+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"272106337625836944827463384317310783253","date":"2026-01-13T13:06:16+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"222425069869769355319373327757407110353","date":"2026-01-13T04:44:55+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"34226834642725475117685403724470527363","date":"2026-01-13T01:06:49+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2026-01-13T00:44:19+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"","date":"2025-11-26T09:50:56+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-11-24T04:32:54+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-11-24T04:32:50+00:00","index":"","fulltext":""},{"type":"submitted","content":"Scientific Reports","date":"2025-11-21T08:55:28+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"scientific-reports","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"scirep","sideBox":"Learn more about [Scientific Reports](http://www.nature.com/srep/)","snPcode":"","submissionUrl":"","title":"Scientific Reports","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Scientific Reports","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"e713827c-d2c8-41d3-b2b5-542c98a639da","owner":[],"postedDate":"January 14th, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[{"id":61070330,"name":"Physical sciences/Engineering"},{"id":61070331,"name":"Earth and environmental sciences/Environmental social sciences"},{"id":61070332,"name":"Physical sciences/Mathematics and computing"}],"tags":[],"updatedAt":"2026-03-30T16:32:03+00:00","versionOfRecord":{"articleIdentity":"rs-8171704","link":"https://doi.org/10.1038/s41598-026-44434-3","journal":{"identity":"scientific-reports","isVorOnly":false,"title":"Scientific Reports"},"publishedOn":"2026-03-26 16:09:36","publishedOnDateReadable":"March 26th, 2026"},"versionCreatedAt":"2026-01-14 12:10:24","video":"","vorDoi":"10.1038/s41598-026-44434-3","vorDoiUrl":"https://doi.org/10.1038/s41598-026-44434-3","workflowStages":[]},"version":"v1","identity":"rs-8171704","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8171704","identity":"rs-8171704","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}