ACCIDENTS AND SAFETY ASSOCIATED WITH INTERCHANGES

The primary objective of this study was to critically review, summarize, and document past safety research that associates accidents and safety with interchange features. Geometric layout, including alignment, ramp types, and interchange areas, and the effects of spacing between interchanges as they relate to accidents are discussed. Collectively, research results indicate that interchange ramps should be designed with flat horizontal curves (except in rural areas), and the maximum degree of curvature for a given design, speed, and superelevation should be avoided. Sharp curves at the ends of ramps and sudden changes from straight alignment to sharp curves should be avoided as well. Ramps of all types and sizes can be designed to connect two or more legs at an interchange. In summary, studies indicate that the design of cloverleaf ramps, scissor ramps, and left-side ramps should be avoided where possible. Collector-distributor roads should be considered in high-volume interchange designs and especially designs in which loop and cloverleaf ramps are used. Interchange areas include the areas along the freeway mainline between and including acceleration lanes, deceleration lanes, and their respective ramps. The relative safety of entrance and exit terminals is enhanced with geometric designs that provide 800-ft or longer acceleration or auxiliary lanes. The same is true for weaving lengths. The potential for accidents has been related to the volume of the ramp and through-lane traffic volumes. Interchange accident rates have been shown to increase as interchange spacing decreased in urban areas. It is concluded that interchange rehabilitation projects are effective in reducing accident experience.

• Record URL:
  http://onlinepubs.trb.org/Onlinepubs/trr/1993/1385/1385-012.pdf
• Record URL:
  https://scholar.google.com/scholar_lookup?title=ACCIDENTS+AND+SAFETY+ASSOCIATED+WITH+INTERCHANGES&author=J.+Twomey&author=M.+Heckman&author=J.+Hayward&author=R.+Zuk&publication_year=1993
• Availability:
  • Find a library where document is available. Order URL: http://worldcat.org/isbn/0309054567
• Supplemental Notes:
  • This paper appears in Transportation Research Record No. 1385, Intersection and Interchange Design. Distribution, posting, or copying of this PDF is strictly prohibited without written permission of the Transportation Research Board of the National Academy of Sciences. Unless otherwise indicated, all materials in this PDF are copyrighted by the National Academy of Sciences. Copyright © National Academy of Sciences. All rights reserved
• Authors:
  • Twomey, James M
  • Heckman, Max L
  • Hayward, John C
  • Zuk, Richard J
• Publication Date: 1993

Language

• English

Media Info

• Features: References; Tables;
• Pagination: p. 100-105
• Monograph Title: Intersection and interchange design
• Serial:
  • Transportation Research Record
  • Issue Number: 1385
  • Publisher: Transportation Research Board
  • ISSN: 0361-1981

Subject/Index Terms

• TRT Terms: Acceleration lanes; Alignment; Auxiliary lanes; Crash rates; Crashes; Curves (Geometry); Geometric design; Interchange ramps; Interchanges; Layout; Length; Ramps; Safety; Spacing; Streets; Traffic volume
• Old TRIS Terms: Collector distributor roads; Freeway entrances and exits
• Subject Areas: Design; Highways; Planning and Forecasting; Safety and Human Factors; I21: Planning of Transport Infrastructure; I81: Accident Statistics; I82: Accidents and Transport Infrastructure;

Filing Info

• Accession Number: 00634568
• Record Type: Publication
• ISBN: 0309054567
• Files: TRIS, TRB, ATRI
• Created Date: Aug 30 1993 12:00AM