Risk-and-Reliability-Based Approaches to Analyzing Road Geometric Design Criteria

Federal and state transportation agencies set goals related to surface transportation system performance. The variability in factors influencing design criteria (e.g., driver performance, road conditions, and vehicle performance) is often large and is addressed implicitly by using “conservative” values. However, a risk-and-reliability-based analysis in roadway geometric design is proposed in this research to address these gaps. Probabilistic geometric design analysis is well suited to explicitly address the level of variability and randomness associated with design inputs when compared with a more deterministic design approach. This research critically assesses alternative approaches for incorporating risk and reliability analysis when establishing road geometric design criteria and design decisions. An in-depth investigation of the applicability of reliability analysis was done and a reliability analysis was used to estimate the probability distribution of operational performance that might result from a basic number of lanes decisions made to achieve a design level of service on a freeway. Geometric effects of freeway ramp spacing and auxiliary lane presence on crash frequency and crash severity were also analyzed. Negative binomial and multinomial logit regression models are used to estimate the effects of ramp spacing and auxiliary lane presence on expected crash frequencies and crash severities, respectively.

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  • Supplemental Notes:
    • This document was sponsored by the U.S. Department of Transportation, University Transportation Centers Program.
  • Corporate Authors:

    University of Utah, Salt Lake City

    Department of Civil and Environmental Engineering
    Salt Lake City, UT  United States 

    Mountain-Plains Consortium

    North Dakota State University
    Fargo, ND  United States  58108

    Office of the Assistant Secretary for Research and Technology

    University Transportation Centers Program
    Department of Transportation
    Washington, DC  United States  20590
  • Authors:
    • Porter, Richard J
    • Musunuru, Anusha
    • Shea, Michael Scott
  • Publication Date: 2019-10


  • English

Media Info

  • Media Type: Digital/other
  • Features: Figures; References; Tables;
  • Pagination: 74p

Subject/Index Terms

Filing Info

  • Accession Number: 01767617
  • Record Type: Publication
  • Report/Paper Numbers: MPC-19-408
  • Contract Numbers: MPC-406
  • Created Date: Mar 23 2021 11:11AM