Phase I Assessment of Guardrail Length-of-Need

Guardrails have commonly been installed to prevent errant vehicles from impacting roadside hazards. However, guardrail impacts have contributed to numerous serious injuries and fatalities, are generally impacted more often when installed closer to the travel way edge , and are usually much longer than the shielded hazard. Thus, in order to reduce the frequency of severe guardrail crashes, an optimized length should be determined. Previously, the American Association of Highway and Transportation Officials Roadside Design Guide (RDG) suggested guardrail runout lengths which were dependent on posted speed limit and traffic volumes, but were considerably longer than those recommended in other studies assessing the optimal length-of-need (LON). Crash data analyses and simulation using the recently-updated Roadside Safety Analysis Program (RSAPv3) was conducted to evaluate the cost- effectiveness and estimated crash costs associated with different guardrail LONs. Crashes involving Kansas guardrail, which were compliant with recommendations provided in the 2006 AASHTO RDG, and occurring on freeways with divided medians were analyzed. The frequency, rate, and risk of shielded hazard crashes were extremely low. RSAPv3 analysis indicated that there was both an economic and safety benefit to reducing the installed LON, as well as utilizing different runout lengths for left- and right-side departures for divided roadways.

  • Record URL:
  • Corporate Authors:

    Midwest Roadside Safety Facility

    2200 Vine Street
    130 Whittier Building
    Lincoln, NE  United States  68588-0853

    University of Nebraska, Lincoln

    Nebraska Transportation Center
    Lincoln, NE  United States  68588

    Wisconsin Department of Transportation

    4802 Sheboygan Avenue
    Madison, WI  United States  53707

    Federal Highway Administration

    1200 New Jersey Avenue, SE
    Washington, DC  United States  20590

    U.S. Department of Transportation

    1200 New Jersey Avenue, SE
    Washington, DC  United States  20590
  • Authors:
    • Albuquerque, Francisco Daniel B
    • Stolle, Cody S
    • Sicking, Dean L
    • Faller, Ronald K
    • Lechtenberg, Karla A
  • Publication Date: 2014-8-12


  • English

Media Info

  • Media Type: Digital/other
  • Edition: Final Report
  • Features: Appendices; Figures; Photos; References; Tables;
  • Pagination: 144p

Subject/Index Terms

Filing Info

  • Accession Number: 01705424
  • Record Type: Publication
  • Report/Paper Numbers: TRP-03-284-14
  • Contract Numbers: TPF-5(193) Supplement #40
  • Created Date: May 3 2019 1:05PM