Turn lanes

Turn lanes are dedicated lanes for left and right turning vehicles

Key characteristics

Setting/Location

All, Corridor, Urban, Suburban, Rural, Neighborhood

Technology

Collaboration

WSDOT regions

Statewide

Other names

  • Left-turn lane
  • Right-turn lane
  • Dedicated turn lane
  • Two-way left turn lane

Strategy description

Turning vehicles can conflict with oncoming traffic, traffic moving in the same direction, pedestrians, bicyclists, or crossing traffic. To reduce conflicts and provide a dedicated space for vehicles, turn lanes provide left-turn and right-turn lanes at intersections to separate turning traffic from through-traffic. Turn lanes also provide space for vehicles to slow down before turning, or speed up after turning.

Turn lanes may also include a shared, two-way left turn lane in the middle of a roadway that separates left-turning traffic from through traffic at mid-block driveways to reduce the chance for rear-end collisions.

When to use this strategy

Turn lanes make sense for:

  • High-speed roadways with a high volume of traffic turning left or right. The turn lanes provide a place for turning traffic to decelerate, yield to oncoming traffic, pedestrians, or bicyclists, and turn safely
  • Intersections with a high volume of left or right turning traffic
  • Intersections with a history of rear-end or turning movement collisions
  • A two-way left turn lane makes sense for multi-lane city streets with left-turning traffic at multiple mid-block driveways

Strategy benefits:

  • Adding or improving turn lanes at intersections improves safety by reducing the possibility of rear-end collisions
  • They can also reduce delays by allowing a dedicated space for turning traffic to wait for a clear path to turn
  • Turn lanes at intersections can also increase capacity for turning vehicles by providing them with a dedicated green signal. However, turn lanes have a couple of disadvantages as well. They increase the width of the roadway, causing pedestrians to have a longer distance to cross and exposing them to traffic for more time. In addition, turn lanes often require adjusted signal timing to provide green time specifically for the turning movements, which increases the delay for pedestrians and bicyclists waiting to cross the road.

What you need in order to implement

Policy needs:

  • Agencies should have design guidelines and warrants for determining when left and right turn lanes should be installed, including when double turn lanes are warranted.

Planning needs:

  • Evaluate turn lane warrants that determine when to install a turn lane
  • Consider if the right-of-way space is available to accommodate the additional roadway width needed to a turn lane
  • Use agency design standards to determine lane width, turn-lane length, deceleration distance, and type of turn movement signal phasing (e.g. protected, permitted, or protected/permitted)

Equipment needs:

  • Dedicated turn lane with painted pavement markings and signs
  • Dedicated turn lane traffic signal head

Maintenance needs:

  •  Maintenance for the turn lane signal heads, signing, and marking

Learn more about this strategy

Federal Highways Administration (FHWA), Signalized intersections: An Informational Guide - Chapter 11 Individual Movement Treatments.

American Association of State Highway and Transportation Officials (AASHTO), A Policy on Geometric Design of Highways and Streets, 7th edition (Fee).

About key characteristics

Location notes:

Turn lanes can be used on any roadway to improve safety by providing space for vehicles slowing to turn, a place to move out of the way of faster-moving traffic in the through travel lanes.

Cost notes:

Cost can require physically widening the road to accommodate an additional turn lane, and it can require modifying a traffic signal to provide traffic signal heads and traffic detection for the new turn lanes.

Technology notes:

Turn lanes at traffic signals will require traffic detectors and traffic signal heads, but otherwise adding turn lanes only requires widening the vehicle roadway to include an additional lane.

Collaboration notes:

Turn lanes require little to no collaboration with partner agencies. The agency may collaborate with the community during the planning process.

Conditions this strategy addresses