Left Turn, U-Turn and Through Restrictions
Purpose
Reduce conflict points at an intersection by restricting left turns, U-turns, or through movements.
Description
Left turn, U-turn, and through restrictions are implemented by signage and sometimes physical barriers (for example, flex posts, wheel stops, etc.) to remove conflicts caused by uncontrolled left turning or through movements at an intersection.
Safety Benefits
- Restricts uncontrolled movements.
- Reduces angle crash risks.
- Can reduce pedestrian and bicycle conflicts.
- Provides a quick to implement safety improvement when a traffic signal project is not possible or while the project progresses.
Street Types and Context
Applicable Street Types
Left turn, U-turn, and through restrictions are applicable to both arterial and local streets.
Other Location Guidance
Left turn, U-turn. and through restrictions should be limited to locations with a history of crashes or crash risks related to the uncontrolled turning movements at the intersection.
Primary User Groups
Key Implementation Considerations
- Left turn, U-turn, and through restrictions require detailed analysis of the movements at an intersection and adjacent intersections prior to design and implementation.
- For intersections with high traffic volumes that provide critical grid connections, left turn, U-turn, and through restrictions may be applied as an interim condition while a larger scale project moves through the funding, design, and construction pipeline.
- Left turn, U-turn. and through restrictions must consider and meet emergency vehicle access requirements.
- Left turn, U-turn. and through restrictions are used to address crash risks at an intersection only. These restrictions are not applicable solely for the purposes of minimizing through traffic or access-related objectives.
Expected Crash Reduction
Reduced crashes by about 60% for studies of No Left Turn, No U-turn, and No Through sign installations. The addition of physical barriers where feasible can further prevent or eliminate crash risks. (Birch and Cottrell, 1994)
Cost
Typically, a low to medium cost treatment. Includes maintenance to upkeep barriers.
Timeline
Typically, left turn, U-turn, and through restrictions can be implemented within a year. Restrictions involve thorough community messaging prior to implementation, as well as in-street notifications through variable messaging signs once installed to alert users of the recent travel pattern changes.
References
