The National Academies

NCHRP 15-27 [Completed]

Safety Impacts of Design Element Trade-Offs

  Project Data
Funds: $449,987
Research Agency: Kentucky Transportation Center--University of Kentucky
Principal Investigator: Nikiforos Stamatiadis
Effective Date: 7/13/2004
Completion Date: 1/31/2009
Comments: The final report is available as NCHRP Report 633.

Design standards provide a benchmark for the development of elements that compose a highway design. Ideally, every highway design would meet the appropriate standards. Realistically, designers are sometimes faced with situations where adherence to standards may not be practical from an engineering, environmental, community, or benefit-cost perspective. In such cases, designers must make decisions regarding the impacts and risks associated with meeting or exceeding the design standards or allowing exceptions to them, for example, in context-sensitive situations. A comprehensive assessment of the safety and operational impacts of trade-offs in design elements can guide designers in weighing appropriate trade-offs in design elements against safety and operational concerns for the full range of highway designs, from low volume to high volume, locals to arterials, and 3-R to new construction.

The objectives of this project were to (1) quantify the safety and operational impacts of design element trade-offs and their associated risks and (2) develop guidelines to assist designers in making reasonable choices among possible design element trade-offs. The project evaluated design element trade-offs encompassing the full range of highway designs, including context-sensitive solutions and common design exceptions.

The project final report is available as NCHRP Report 633, Impact of Shoulder Width and Median Width on Safety.


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