The National Academies

NCHRP 15-64 [Final]

Guidelines for the Design of Unsignalized Median Openings in Close Proximity to Signalized Intersections

  Project Data
Funds: $325,000
Research Agency: Texas A&M Transportation Institute
Principal Investigator: Karen Dixon, Ph.D.
Effective Date: 8/22/2016
Completion Date: 8/22/2018

NCHRP Research Report 929 presents state departments of transportation and other transportation agencies with a quantifiable approach for evaluating the operational and safety performance associated with unsignalized full median openings located near upstream and downstream traffic signals that have at least one turning bay. The report also provides guidelines for evaluating the performance of other median opening configurations. The material in this report will be of immediate interest to traffic engineers and other practitioners responsible for implementing unsignalized median openings to improve operations at a signalized intersection.


Many agencies discourage access within the functional area of a signalized intersection, as recommended in current access management guidelines, which also suggests that unsignalized median openings be bidirectional openings designed for left-turns from the roadway (and possibly U-turns) only. Closely spaced median openings can result in a complex pattern of overlapping conflicts and a resulting range of safety and operational impacts, while full access intersections may be unnecessary and result in negative impacts on traffic operations. Managing access in most cases is the best solution; however, there are few guidelines on what parameters an agency should consider when selecting between full versus restricted access medians. In addition, removing movements reduces conflict points and when located and designed correctly, an unsignalized median opening may improve operations at a signalized intersection. There was a need to provide guidelines on the design of median openings to improve safety and operations of these access points.


Under NCHRP Project 15-64, the Texas A&M Transportation Institute developed guidelines for transportation agencies to evaluate the safety and operational effects of the location and design of unsignalized median openings in close proximity to signalized intersections.


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