Evaluating the Effects of Freeway Design Elements on Safety

Increased emphasis has been placed on improving the explicit role of highway safety in making decisions on highway planning, design, and operations. This end can be achieved by quantifying the safety effects of geometric design elements for various highway facilities. The objective of this study was to investigate the safety effects of two important design elements for freeways: ramp density and horizontal curve. Data available for use in the evaluation included 324.2 centerline mi of freeways collected in Texas. Five years (1997–2001) of freeway crashes were examined. Negative binomial regression models were used to estimate the effects of independent variables on crashes. The final model for evaluation revealed that crashes on freeway segments were associated with average daily traffic, on-ramp density, degree of curvature, median width with inside shoulder, the number of lanes (for urban freeways), and whether the freeway is in an urban or rural area. Off-ramp density was not statistically significant in the model. Furthermore, the effect of on-ramp density on freeway crashes was significant for horizontal curves but not for tangent sections and indicates that freeway designers should eliminate or minimize the number of on-ramps within the horizontal curves. The statistical modeling results were geared into the development of accident modification factors for on-ramp density and horizontal curves that can be used for safety prediction of freeways.

• Record URL:
  https://doi.org/10.3141/2195-07
• Summary URL:
  http://scholar.google.com/scholar_lookup?title=Evaluating+the+Effects+of+Freeway+Design+Elements+on+Safety&author=B.+Park&author=K.+Fitzpatrick&author=D.+Lord&publication_year=2010
• Availability:
  • Find a library where document is available. Order URL: http://www.trb.org/Main/Blurbs/Highway_Design_2010_165053.aspx
• Authors:
  • Park, Byung-Jung
  • Fitzpatrick, Kay
  • Lord, Dominique
• Publication Date: 2010

Language

• English

Media Info

• Media Type: Print
• Features: Figures; References; Tables;
• Pagination: pp 58-69
• Monograph Title: Highway Design 2010
• Serial:
  • Transportation Research Record: Journal of the Transportation Research Board
  • Issue Number: 2195
  • Publisher: Transportation Research Board
  • ISSN: 0361-1981

Subject/Index Terms

• TRT Terms: Crash modification factors; Freeways; Geometric design; Highway curves; Highway design; Highway safety; Mathematical models; On ramps; Traffic crashes
• Uncontrolled Terms: Horizontal curvature; Negative binomial regression
• Geographic Terms: Texas
• Subject Areas: Design; Highways; Safety and Human Factors; I20: Design and Planning of Transport Infrastructure;

Filing Info

• Accession Number: 01157692
• Record Type: Publication
• ISBN: 9780309160711
• Report/Paper Numbers: 10-2979
• Files: TRIS, TRB, ATRI
• Created Date: May 30 2010 7:44AM