The National Academies

NCHRP 15-14(2) [Completed]

Median Intersection Design

  Project Data
Funds: $350,000
Research Agency: Midwest Research Institute
Principal Investigator: Douglas W. Harwood
Effective Date: 12/1/1992
Completion Date: 6/15/1995

Although median widths on limited access highways based on the safety requirements of motorists traveling under freeway conditions have been well researched, similar reasoned conclusions about median widths at divided highway intersections with partial or no access control were lacking before this project was undertaken.

Operational problems near median intersections mandate different considerations than those applicable to limited access highway medians. This research project evaluated all of the operational problems that occur at such intersections. Such research is particularly pertinent now that many transportation agencies are focusing on constructing or reconstructing multilane facilities that have partial or no access control.

Midwest Research Institute developed and recommended median-width parameters and design criteria for intersections considering safety, traffic operations, traffic volumes, type of traffic control, facility design speed, and traffic characteristics. The research found that at rural unsignalized intersections, i.e., those with divided highway volume greater than 7,000 veh/day or speeds higher than 50 mph, both accidents and undesirable driving behavior decrease as the median width increases. Conversely, at suburban signalized and unsignalized intersections, accidents and undesirable behavior increase as the median width increases. When these design criteria are adopted, state and local transportation agencies should be able to design and construct medians for divided highways with partial or no access control at intersections with the same degree of confidence they have when designing medians under freeway conditions. The research findings have been published in NCHRP Report 375, Median Intersection Design.

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