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Portland Bureau of Transportation

We keep Portland moving

Phone: 503-823-5185

Fax: 503-823-7576

1120 SW Fifth Ave, Suite 800, Portland, OR 97204

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Traffic Circles

 

Description:

Traffic circles are raised islands placed in an intersection. They are landscaped with ground cover and street trees. Traffic circles require drivers to slow to a speed that allows them to comfortably maneuver around them.

Purpose:

The primary benefit of traffic circles is they reduce the number of angle and turning collisions. An additional benefit is they slow high-speed traffic.

Effectiveness:

Traffic circles are very effective at lowering speeds in their immediate vicinity. Traffic circles are most effective when constructed in a series on a local service street.
 
Advantages Disadvantages
Effectively reduce vehicle speeds
 
Improve safety conditions (for example, there are fewer left-hand turn crashes involving other vehicles)
 
Visually attractive
Require some parking removal
 
Can cause bicycle/auto conflicts at intersections because of narrowed travel lane
 
Can restrict emergency or transit vehicle movement if vehicles are parked illegally near the circle

Cost:

Traffic circles cost approximately $5,000 to $15,000 each.

Parking Impacts:

A minimum of 30 feet of curbside parking must be prohibited on the through street at each corner of the intersection.

Transit Service Impacts:

Tri Met buses can maneuver around traffic circles at slow speeds provided vehicles are not illegally parked near the circles.

Emergency Services Impacts:

Fire trucks can maneuver around traffic circles at slow speeds provided vehicles are not illegally parked near the circles.

Noise Impacts:

Noise impacts are minimal. There may be some noise related to vehicles decelerating and accelerating near the circles.

Other Considerations:

If well-maintained, traffic circles can be very attractive. However, there are also a lot of traffic control signs and pavement markings associated with circles that are not so attractive.
 
Traffic circles are less effective at T-intersections and difficult to design for offset intersections.

Examples In Portland:

SE Lincoln/Harrison, between 20th and 60th Ave. SE Clinton, between 12th and 52nd Ave. NE 15th, north of Broadway.