Prohibiting left-turns at intersections can reduce the risk of motorists failing to yield to pedestrians. Source: Flickr - M.V. Jantzen (2008)

Left Turn Prohibitions

Left-turn prohibitions use a raised measure to physically prohibit left-turns at specific locations where the turning vehicle may present a conflict with pedestrians in the crosswalk. Ideally, the design of this measure should allow for easy access by bicyclists and all pedestrians who are crossing the street perpendicular to the measure.

As with other traffic management tools, left-turn prohibitions must be used in conjunction with other traffic management tools within the neighborhood street network. The result of this measure may also reduce the through-traffic of the cross-street, however additional right-turns and increased traffic at proximate intersections may occur.

Purpose

Left-turns at intersections can present a challenge to motorists who must yield to both oncoming traffic and crossing pedestrians to find an acceptable gap. This situation increases the crash risk for pedestrians who may be struck by motorists that fail to yield. Prohibiting left-turns through physical measures is one method to nearly eliminate this risk.

Considerations

• Impacts residents more than through traffic.
• Evaluate traffic patterns to determine whether other streets would be adversely affected due to an increase in right turns.
• Prohibitions generally do not effectively address midblock speeding problems.
• Prohibitions should have strong neighborhood support.
• The effect of diverters on service vehicles should be considered.
• Do not adversely affect access by service vehicles.
• Analyze whether less restrictive measures such as time-of-day prohibitions would work.
• Will create out-of-the-way travel for residents and put additional traffic on other streets.
• Consider impact on school bus routes, emergency access, and trash pickup.

Estimated Cost

If a raised median is installed, the cost can range from $10,000 to $30,000 per 100 feet. Adding other traffic measures can significantly raise the cost.

Case Studies

Eureka, California
New York, New York

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