Mitigation Strategies for Design Exceptions

Design criteria, established through years of practice and research, form the basis by which highway designers strive to balance cost, safety, mobility, social and environmental impacts, and the needs of a wide variety of roadway users. For many situations, there is sufficient flexibility within the design criteria to achieve a balanced design and still meet minimum values. On occasion, designers encounter situations in which the appropriate solution may suggest that using a design value or dimension outside the normal range of practice is necessary. In these cases, a design exception may be considered. A design exception is a documented decision to design a highway element or a segment of highway to design criteria that do not meet minimum values or ranges established for that highway or project. This publication provides detailed information on design exceptions and mitigating the potential adverse impacts to highway safety and traffic operations. Chapter 1 provides basic information on design exceptions. Also discussed are the concepts of nominal and substantive safety, which are fundamental to the topic of design exceptions, their mitigation, and decision making. Chapter 2 discusses the steps of an effective design exception process. Chapter 3 clarifies the 13 controlling criteria, including when design exceptions are required, how safety and operations are affected by the 13 controlling criteria, and what the potential adverse impacts are if design criteria are not met. Information on substantive safety is provided where available. Chapter 4 presents and illustrates potential mitigation strategies. Chapters 5 through 8 are case studies that illustrate how several States have effectively approached projects with difficult site constraints and design exceptions, including implementation of mitigation strategies.

• Record URL:
  http://www.wsdot.wa.gov/publications/fulltext/ProjectDev/Manuals/MitigationManual.pdf
• 
• Corporate Authors:

  CH2M HILL

  1295 Northland Drive, Suite 200
  Mendota Heights, MN  United States  55120

  Federal Highway Administration

  Office of Safety, 1200 New Jersey Avenue, SE
  Washington, DC  United States  20590
• Authors:
  • Stein, William J
  • Neuman, Timothy R
• Publication Date: 2007-7

Language

• English

Media Info

• Media Type: Web
• Features: Bibliography; Figures; Tables;
• Pagination: 174p

Subject/Index Terms

• TRT Terms: Highway design; Highway operations; Highway safety; Impacts; Strategic planning
• Uncontrolled Terms: Design exceptions; Mitigation strategies
• Subject Areas: Design; Highways; I20: Design and Planning of Transport Infrastructure;

Filing Info

• Accession Number: 01121736
• Record Type: Publication
• Report/Paper Numbers: FHWA-SA-07-011
• Contract Numbers: DTFH61-05-D-00125
• Files: TRIS, USDOT
• Created Date: Feb 17 2009 12:30PM