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 American Association of State Highway and Transportation Officials' (AASHTO's) Strategic Plan, for example, includes goals to cut fatalities in half by 2030, create a congestion free surface transportation system, and improve system performance (AASHTO, 2009). Policies and procedures that explicitly consider performance goals at all organizational levels in transportation agencies will maximize the likelihood they are achieved. Performance measures are being used to increase accountability for how highway funds are being spent (FHWA, 2012). Moving Ahead for Progress in the 21st Century Act (MAP-21) establishes a performance-based Federal highway program, where investment decisions are made through performance-based planning and programming. States are expected to invest resources in projects that achieve performance targets and collectively contribute to achieving national performance goals. Once funds are allocated, road design activities and decisions should be consistent with performance goals set during planning and programming. A performance-based design approach would be a significant contribution to achieving performance objectives and making well-informed design decisions. FHWA has recently formed a task force to explore the transition from a criteria-based road design to performance-based road design. The Transportation Research Board's (TRB's) Operational Effects of Geometric Committee (AHB65) created a Subcommittee on Performance-Based Analysis to investigate processes and procedures to incorporate safety and operational performance prediction into the project development process. Current highway geometric design processes require establishment of fundamental design controls (e.g. area type, terrain, functional classification, design vehicle, traffic volume) and selection of design speed. The process then becomes dimensionally-based, with minimums, maximums and ranges in design values directly derived from tables, charts and equations. Acceptable performance in terms of mobility and safety is presumed to result from proper application of design criteria. 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. This can lead to performance outcomes that are different than intended (Porter et al., 2012). The relative likelihoods (or probabilities) that design alternatives will meet transportation performance goals throughout their life cycles are not explicitly or quantitatively evaluated. A risk and reliability-based highway geometric design approach is a possible solution to address these gaps. This idea has received national interest, evident from an invited TRB podium session at the 2012 annual meeting, "Risk and Reliability Analysis in Geometric Design of Highways and Streets." Design approaches based on levels of risk (the probability of an event occurring and the impact that the event will have on the achievement of design, project or agency objectives) and reliability (the ability of a system to consistently do what it was expected or designed to do) are currently used in several engineering/technical disciplines (e.g., structural design, hydrology and hydraulics, systems engineering and management). This project will provide a strategic step towards development of road design processes that: 1) explicitly consider and quantify the variability and uncertainty in factors that influence design criteria and design decisions; and 2) explicitly incorporate expected performance outcomes and the uncertainty of performance predictions into design decisions.


  • English


  • Status: Completed
  • Funding: $209761
  • Contract Numbers:


  • Sponsor Organizations:

    Research and Innovative Technology Administration

    University Transportation Centers Program
    1200 New Jersey Avenue, SE
    Washington, DC  United States  20590
  • Managing Organizations:

    Mountain-Plains Consortium

    North Dakota State University
    Fargo, ND  United States  58108
  • Project Managers:

    Tolliver, Denver

  • Performing Organizations:

    Dept. of Civil and Environmental Engineering

    University of Utah
    Salt Lake City, UT  United States 
  • Principal Investigators:

    Porter, Richard

  • Start Date: 20120101
  • Expected Completion Date: 20190930
  • Actual Completion Date: 20210301
  • USDOT Program: University Transportation Centers Program
  • Source Data: MPC-406

Subject/Index Terms

Filing Info

  • Accession Number: 01483224
  • Record Type: Research project
  • Source Agency: Mountain-Plains Consortium
  • Contract Numbers: DTRT12-G-UTC08
  • Files: UTC, RIP
  • Created Date: Jun 6 2013 1:01AM