[{"data":1,"prerenderedAt":-1},["ShallowReactive",2],{"doc-seo-657892-105":3,"detail-sidebar-cat-0-en-105":80,"doc-detail-657892-en":130},{"code":4,"msg":5,"data":6},0,"ok",{"site_id":7,"language":8,"slug":9,"title":10,"keywords":11,"description":12,"schema_data":13,"social_meta":73,"head_meta":75,"extra_data":77,"updated_unix":79},105,"en","213-modern-roundabouts-geometric-layout-design-criteria","213 Modern Roundabouts - Geometric Layout Design Criteria","","Chapter 213.1–213.3 outlines design criteria for the geometric layout and safe operation of modern roundabouts. It specifies which lane configurations are appropriate, how roundabout evaluation follows the Intersection Control Evaluation process, and how operational analysis should use current Highway Capacity Manual methodology with consistent HCM-mode software. It recommends lane provisioning based on warranted needs, uses 20-year design traffic volumes, and addresses stage construction logic. It also details speed-calming geometric features such as central island landscaping, splitter islands, curvature and deflection, typical ICD ranges, and high-speed approach geometry.",{"@graph":14,"@context":72},[15,34,55],{"@type":16,"itemListElement":17},"BreadcrumbList",[18,23,27,31],{"item":19,"name":20,"@type":21,"position":22},"https://docshare.wps.com","Home","ListItem",1,{"item":24,"name":25,"@type":21,"position":26},"https://docshare.wps.com/document/","Document",2,{"item":28,"name":29,"@type":21,"position":30},"https://docshare.wps.com/document/research-report/","Research & Report",3,{"item":32,"name":10,"@type":21,"position":33},"https://docshare.wps.com/document/213-modern-roundabouts-geometric-layout-design-criteria/657892/",4,{"url":32,"name":10,"@type":35,"image":36,"author":41,"headline":10,"publisher":44,"fileFormat":47,"inLanguage":8,"description":12,"dateModified":48,"datePublished":49,"encodingFormat":47,"isAccessibleForFree":50,"interactionStatistic":51},"DigitalDocument",{"url":37,"@type":38,"width":39,"height":40},"https://docshare.wps.com/thumbnails/213-modern-roundabouts-geometric-layout-design-criteria/657892.png","ImageObject",300,407,{"name":42,"@type":43},"Terk","Person",{"url":19,"name":45,"@type":46},"DocShare","Organization","application/pdf","2026-10-30","2026-10-26",true,{"@type":52,"interactionType":53,"userInteractionCount":33},"InteractionCounter",{"@type":54},"ViewAction",{"@type":56,"mainEntity":57},"FAQPage",[58,64,68],{"name":59,"@type":60,"acceptedAnswer":61},"What lane types are intended for modern roundabout construction on the SHS?","Question",{"text":62,"@type":63},"Only single-lane and two-lane modern roundabouts are to be constructed on the SHS. Partial three-lane roundabouts may be acceptable under certain conditions.","Answer",{"name":65,"@type":60,"acceptedAnswer":66},"Which methodology and software approach should be used for roundabout operational analysis?",{"text":67,"@type":63},"Use the current Highway Capacity Manual (HCM) methodology. Common software packages consistent with HCM are HCS and SIDRA; when using SIDRA, run analysis in HCM mode to remain consistent.",{"name":69,"@type":60,"acceptedAnswer":70},"Why should stage construction be considered, and how should the designs be developed?",{"text":71,"@type":63},"Stage construction is considered when analysis indicates a multi-lane roundabout is required in the design year but a single-lane configuration would provide acceptable service for 10–15 years. When staging is used, develop the ultimate design first to confirm right-of-way needs, then develop an initial design that allows future expansion with minimal throw-away work.","https://schema.org",{"og:url":32,"og:type":74,"og:title":10,"og:site_name":45,"og:description":12},"article",{"robots":76,"canonical":32},"index,follow",{"doc_id":78,"site_id":7},657892,1793101516,{"code":4,"msg":81,"data":82},"success",[83,87,91,95,100,105,110,114,119,122,126],{"id":22,"doc_module":4,"doc_module_name":25,"category_name":84,"show_sort_weight":85,"slug":86},"Story & Novel",90,"story-novel",{"id":26,"doc_module":4,"doc_module_name":25,"category_name":88,"show_sort_weight":89,"slug":90},"Literature",80,"literature",{"id":33,"doc_module":4,"doc_module_name":25,"category_name":92,"show_sort_weight":93,"slug":94},"Exam",70,"exam",{"id":96,"doc_module":4,"doc_module_name":25,"category_name":97,"show_sort_weight":98,"slug":99},5,"Comic",60,"comic",{"id":101,"doc_module":4,"doc_module_name":25,"category_name":102,"show_sort_weight":103,"slug":104},6,"Technology",50,"technology",{"id":106,"doc_module":4,"doc_module_name":25,"category_name":107,"show_sort_weight":108,"slug":109},7,"Healthcare",40,"healthcare",{"id":111,"doc_module":4,"doc_module_name":25,"category_name":29,"show_sort_weight":112,"slug":113},8,30,"research-report",{"id":115,"doc_module":4,"doc_module_name":25,"category_name":116,"show_sort_weight":117,"slug":118},9,"Religion & Spirituality",20,"religion-spirituality",{"id":117,"doc_module":4,"doc_module_name":25,"category_name":120,"show_sort_weight":117,"slug":121},"World Cup","world-cup",{"id":123,"doc_module":4,"doc_module_name":25,"category_name":124,"show_sort_weight":123,"slug":125},10,"Lifestyle","lifestyle",{"id":127,"doc_module":4,"doc_module_name":25,"category_name":128,"show_sort_weight":96,"slug":129},19,"General","general",{"code":4,"msg":81,"data":131},{"doc_id":78,"user_id":132,"nickname":42,"user_avatar":133,"doc_module":4,"category_id":111,"category_name":29,"doc_title":10,"doc_description":12,"doc_content":134,"file_id":135,"file_url":136,"file_type":137,"file_size":138,"view_count":33,"is_deleted":4,"is_public":22,"is_downloadable":22,"audit_status":22,"page_count":139,"language":140,"language_code":8,"site_id":7,"html_lang":8,"table_of_contents":141,"faqs":142,"seo_title":143,"seo_description":12,"update_tm":144,"read_time":98},1099525198933,"https://ap-avatar.wpscdn.com/davatar_155a257f0dc6eb9ab79c44ca47cae57d","213 Modern Roundabouts  \n213.1 General  \nThis chapter provides design criteria for the geometric layout of modern roundabouts. The criteria contained in the FDM are supplemented by guidance provided in the National Cooperative Highway Research Program (NCHRP) Report 672, Roundabouts: An  \nInformational Guide.  \nOnly single-lane and two-lane modern roundabouts are to be constructed on the SHS. Partial three-lane roundabouts may be acceptable under certain conditions.  \nExhibit 213-1 illustrates the elements of a modern roundabout that are discussed in this chapter.  \n213.1.1 Roundabout Evaluation  \nRoundabout evaluation is governed by the Intersection Control Evaluation process. Seethe Intersection Control Evaluation (ICE) Manual for requirements at the following web address:  \n[https://www.fdot.gov/traffic/TrafficServices/Intersection_Operations.shtm](https://www.fdot.gov/traffic/TrafficServices/Intersection_Operations.shtm)  \n213-Modern Roundabouts  \n213.2 Operational Analysis  \nUse the methodology in the current edition of the Highway Capacity Manual (HCM) when conducting a roundabout operational analysis. Two commonly used software packages consistent with the HCM are HCS and SIDRA. When SIDRA is used, run the analysis in HCM mode to be consistent with HCM methodology. For more information on HCS and SIDRA, see Traffic Analysis Handbook, Chapter 6.  \nTo optimize safety and operation performance, provide only the lanes that are warranted through the traffic operational analysis. Inclusion of unwarranted approach, circulatory or by-pass lanes increases complexity and conflict points. Provide roundabout designs that are simplistic and have pavement widths based on necessity.  \nUse 20-year design traffic volumes for roundabout design.  \n213.2.1 Stage Construction  \nConsider stage construction when traffic operational analysis indicates that a multi-lane roundabout will be required in the design year (20-year design life) , but a single-lane roundabout would provide acceptable service for 10 to 15 years (1st resurfacing cycle) . Having more lanes than what is warranted in the early years will have a negative effect on safety and operational performance.  \nWhen it is determined that staged construction will be utilized, develop the ultimate design first to assure all right-of-way needs for the ultimate project are identified. Then develop the initial design that allows for expansion in the future with minimal “throw-away” work.  \n213.3 Geometric Design  \nIt is important to develop roadway geometry that encourages drivers to gradually slowdown as they approach the roundabout. Roundabout design features that influence vehicular approach speeds include:  \n(1) Prominent landscaping in the central island serves to increase visibility of the central island and provides a visual queue to approaching drivers that they are entering a low-speed environment. Roadway approach geometry should work with the landscaping to limit line of sight beyond what is necessary to meet intersection sight distance requirements. See NCHRP Report 672, 6.7.3 for additional information.  \n213-Modern Roundabouts  \n(2) Raised splitter islands and roadside curb provide visual ques to establish a speed transition zone. Lengthening this transition zone on high-speed facilities can bean effective strategy for slowing down traffic prior to entering a roundabout.  \n(3) Geometric features (e.g. , inscribed circle diameter (ICD) , lane width, entry width, curb locations) introduce deflection and curvature into the driver’s path and is the most effective way to slow vehicles down to a safe entry speed.  \nTypical ranges are as follows:  \n(a) Single-lane Roundabout ICD: 120’ to 160’ with 140’ as a good starting point  \n(b) Two-lane Roundabout ICD: 160’ to 200’ with 180’ as a good starting point A chicane is a series of curves that requires the driver to turn slightly right and then slightly left while approaching the roundabout entry. Chicaning should not be excessive but ","cbCaiiIBt5Qz77iG","https://ap.wps.com/l/cbCaiiIBt5Qz77iG","pdf",1441564,24,"English","# 213.1 General\n## 213.1.1 Roundabout Evaluation\n# 213.2 Operational Analysis\n## 213.2.1 Stage Construction\n# 213.3 Geometric Design\n## 213.3.1 High-Speed Approach Geometry","[{\"question\":\"What lane types are intended for modern roundabout construction on the SHS?\",\"answer\":\"Only single-lane and two-lane modern roundabouts are to be constructed on the SHS. Partial three-lane roundabouts may be acceptable under certain conditions.\"},{\"question\":\"Which methodology and software approach should be used for roundabout operational analysis?\",\"answer\":\"Use the current Highway Capacity Manual (HCM) methodology. Common software packages consistent with HCM are HCS and SIDRA; when using SIDRA, run analysis in HCM mode to remain consistent.\"},{\"question\":\"Why should stage construction be considered, and how should the designs be developed?\",\"answer\":\"Stage construction is considered when analysis indicates a multi-lane roundabout is required in the design year but a single-lane configuration would provide acceptable service for 10–15 years. When staging is used, develop the ultimate design first to confirm right-of-way needs, then develop an initial design that allows future expansion with minimal throw-away work.\"}]","213 Modern Roundabouts - Geometric Layout Design Criteria | PDF",1792993662]