Balancing Accessibility and Equity in EMS Resource Allocation: A Spatial Optimization Perspective

Balancing Accessibility and Equity in EMS Resource Allocation: A Spatial Optimization Perspective | 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 Balancing Accessibility and Equity in EMS Resource Allocation: A Spatial Optimization Perspective Ge Gao, Yong Zhao, Wenkai Xu, Huijun Sun, Zhaokun Wei This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7135511/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 8 You are reading this latest preprint version Abstract Background Emergency Medical Services (EMS) play a crucial role within the broader field of emergency medicine. Efficient resource allocation is vital to ensure timely access to care and equitable service distribution. However, when resources are allocated inefficiently, service areas can become either excessively large or overlap. Oversized service radii can delay response times, while overly small radii result in the inefficient concentration of resources, ultimately compromising service equity. Thus, optimizing the allocation of EMS resources is essential to improve both response times and fairness in service delivery. Methods This study integrates the spatial characteristics of supply and demand in EMS systems and employs accessibility-based measures to optimize resource allocation, aiming to improve both accessibility and equity. A Supply-Demand Three-Step Floating Catchment Area (SD3SFCA) model is developed to evaluate service levels. Based on this, a static bi-objective optimization model is constructed-balancing accessibility and equity-and solved using the NSGA-II algorithm. Model performance is examined under varying impedance coefficients to assess robustness and effectiveness. Results The results reveal that accessibility improves with increased investment in emergency facilities, eventually reaching a plateau. In contrast, equity follows an inverted U-shaped pattern—rising initially and then declining. Under equal equity levels, lower impedance values correspond to higher accessibility, indicating an inverse relationship between impedance and accessibility. Similarly, under equal accessibility levels, equity improves with lower impedance before congestion effects emerge. Furthermore, lower impedance coefficients yield more Pareto-optimal solutions within acceptable bounds, while higher impedance limits solution diversity and leads to suboptimal outcomes near the edge of feasibility. Conclusions These results underscore the importance of low-impedance transportation environments-achievable through infrastructure upgrades or EMS traffic prioritization-in improving both accessibility and equity. The proposed SD3SFCA-based bi-objective optimization model demonstrates strong robustness across varying urban contexts, offering a theoretically sound and practically applicable framework for the planning and evaluation of pre-hospital emergency medical transport systems. Pre-hospital emergency medical services Accessibility Floating catchment area model Equity Full Text Additional Declarations No competing interests reported. Cite Share Download PDF Status: Under Review Version 1 posted Reviews received at journal 29 Sep, 2025 Reviewers agreed at journal 19 Aug, 2025 Reviewers agreed at journal 14 Aug, 2025 Reviewers invited by journal 14 Aug, 2025 Editor assigned by journal 13 Aug, 2025 Editor invited by journal 23 Jul, 2025 Submission checks completed at journal 22 Jul, 2025 First submitted to journal 22 Jul, 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-7135511","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":502696344,"identity":"f374db25-2595-4ce9-9ecc-d28b389a1e48","order_by":0,"name":"Ge Gao","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA4klEQVRIiWNgGAWjYNACAxsGhgNgFjOxWgrSQFoYG0jQ8uEwCVrk3Q8ffvHB4Lw934305w8YKqwTG9jPHsCrxfBMWprlDIPbiTNv5Bg2MJxJT2zgyUvAr6Uhx8yYx+B2gsGNHMYGxrbDiQ0SPAb4tfS/MTP+Y3DO3uBG+sMGxn9EaJGXyDF+zGBwgHHDjQTDBsYGIrQYSDxLY+wxSE6ceeaN4YyEY+nGbTw5BGzpTz784ccfO3u+4+kPPnyosZbtZz9DwJYDDGwScF4CELPhVQ+ypYGB+QMhRaNgFIyCUTDCAQD1Ckv9QIBetAAAAABJRU5ErkJggg==","orcid":"","institution":"Shandong University of Science and Technology","correspondingAuthor":true,"prefix":"","firstName":"Ge","middleName":"","lastName":"Gao","suffix":""},{"id":502696345,"identity":"0852a4e9-b5d1-41d8-964c-3661acadfc6e","order_by":1,"name":"Yong Zhao","email":"","orcid":"","institution":"Shandong University of Science and Technology","correspondingAuthor":false,"prefix":"","firstName":"Yong","middleName":"","lastName":"Zhao","suffix":""},{"id":502696346,"identity":"c6671c6a-aa26-4661-829f-cd067f51e77a","order_by":2,"name":"Wenkai Xu","email":"","orcid":"","institution":"Shandong University of Science and Technology","correspondingAuthor":false,"prefix":"","firstName":"Wenkai","middleName":"","lastName":"Xu","suffix":""},{"id":502696347,"identity":"38661563-f313-40ae-96bb-a6bc4866eb30","order_by":3,"name":"Huijun Sun","email":"","orcid":"","institution":"Beijing jiaotong University","correspondingAuthor":false,"prefix":"","firstName":"Huijun","middleName":"","lastName":"Sun","suffix":""},{"id":502696348,"identity":"0ac23d60-c26b-4a58-bcee-23b625c7fa77","order_by":4,"name":"Zhaokun Wei","email":"","orcid":"","institution":"Shandong University of Science and Technology","correspondingAuthor":false,"prefix":"","firstName":"Zhaokun","middleName":"","lastName":"Wei","suffix":""}],"badges":[],"createdAt":"2025-07-16 04:08:08","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-7135511/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-7135511/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":89652827,"identity":"16063b7b-c76b-4018-a518-555d034cab62","added_by":"auto","created_at":"2025-08-22 10:03:26","extension":"pdf","order_by":1,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":878283,"visible":true,"origin":"","legend":"","description":"","filename":"Manuscript2025.7.22.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7135511/v1_covered_2fbf653b-d1b2-45a5-8886-50456502ca87.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Balancing Accessibility and Equity in EMS Resource Allocation: A Spatial Optimization Perspective","fulltext":[],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":false,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":true,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":true,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"bmc-health-services-research","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"bhsr","sideBox":"Learn more about [BMC Health Services Research](http://bmchealthservres.biomedcentral.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/BHSR/default.aspx","title":"BMC Health Services Research","twitterHandle":"BMC_series","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"em","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"Pre-hospital emergency medical services, Accessibility, Floating catchment area model, Equity","lastPublishedDoi":"10.21203/rs.3.rs-7135511/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7135511/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003ch2\u003eBackground\u003c/h2\u003e\u003cp\u003eEmergency Medical Services (EMS) play a crucial role within the broader field of emergency medicine. Efficient resource allocation is vital to ensure timely access to care and equitable service distribution. However, when resources are allocated inefficiently, service areas can become either excessively large or overlap. Oversized service radii can delay response times, while overly small radii result in the inefficient concentration of resources, ultimately compromising service equity. Thus, optimizing the allocation of EMS resources is essential to improve both response times and fairness in service delivery.\u003c/p\u003e\u003ch2\u003eMethods\u003c/h2\u003e\u003cp\u003eThis study integrates the spatial characteristics of supply and demand in EMS systems and employs accessibility-based measures to optimize resource allocation, aiming to improve both accessibility and equity. A Supply-Demand Three-Step Floating Catchment Area (SD3SFCA) model is developed to evaluate service levels. Based on this, a static bi-objective optimization model is constructed-balancing accessibility and equity-and solved using the NSGA-II algorithm. Model performance is examined under varying impedance coefficients to assess robustness and effectiveness.\u003c/p\u003e\u003ch2\u003eResults\u003c/h2\u003e\u003cp\u003eThe results reveal that accessibility improves with increased investment in emergency facilities, eventually reaching a plateau. In contrast, equity follows an inverted U-shaped pattern\u0026mdash;rising initially and then declining. Under equal equity levels, lower impedance values correspond to higher accessibility, indicating an inverse relationship between impedance and accessibility. Similarly, under equal accessibility levels, equity improves with lower impedance before congestion effects emerge. Furthermore, lower impedance coefficients yield more Pareto-optimal solutions within acceptable bounds, while higher impedance limits solution diversity and leads to suboptimal outcomes near the edge of feasibility.\u003c/p\u003e\u003ch2\u003eConclusions\u003c/h2\u003e\u003cp\u003eThese results underscore the importance of low-impedance transportation environments-achievable through infrastructure upgrades or EMS traffic prioritization-in improving both accessibility and equity. The proposed SD3SFCA-based bi-objective optimization model demonstrates strong robustness across varying urban contexts, offering a theoretically sound and practically applicable framework for the planning and evaluation of pre-hospital emergency medical transport systems.\u003c/p\u003e","manuscriptTitle":"Balancing Accessibility and Equity in EMS Resource Allocation: A Spatial Optimization Perspective","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-08-22 09:31:19","doi":"10.21203/rs.3.rs-7135511/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"editorInvitedReview","content":"","date":"2025-09-29T10:53:26+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"143842592898654149479731323514083151727","date":"2025-08-19T14:37:13+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"25191279589315862687413797599987623124","date":"2025-08-14T15:11:03+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-08-14T14:24:06+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-08-13T06:18:28+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"","date":"2025-07-23T09:47:21+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-07-22T13:44:49+00:00","index":"","fulltext":""},{"type":"submitted","content":"BMC Health Services Research","date":"2025-07-22T13:40:33+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"bmc-health-services-research","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"bhsr","sideBox":"Learn more about [BMC Health Services Research](http://bmchealthservres.biomedcentral.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/BHSR/default.aspx","title":"BMC Health Services Research","twitterHandle":"BMC_series","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"em","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"b2ba35af-f90e-4c01-b4e9-61eeeae00bbb","owner":[],"postedDate":"August 22nd, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2025-08-22T09:31:20+00:00","versionOfRecord":[],"versionCreatedAt":"2025-08-22 09:31:19","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-7135511","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7135511","identity":"rs-7135511","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}