Roundabouts are one option used for traffic control at an
intersection. The Ada County Highway District has constructed
several roundabouts and more are proposed or being evaluated at
various intersections around the county.
Benefits of Roundabouts
- Improve safety
- Provide better traffic flow and reduced delay
- Fewer vehicle conflict points than a traditional intersection
- Business and community enhancement
- Decrease air pollution - emissions are reduced by avoiding frequent starts and stops
Click on the image at the right to view the features of a basic roundabout.
Roundabouts and safety
Roundabouts typically eliminate the most severe intersection
accidents — T-bones and head-on collisions. They have fewer vehicle
conflict points than a traditional intersection which results in 48%
less accidents than signalized intersections and 78% less injury and
fatal crashes than signalized intersections.*
How to use a roundabout
Read below to learn more about using a roundabout as a motorist,
bicyclist, or pedestrian.
- Slow down
- Enter appropriate lane if there are multiple lanes.
- Yield to pedestrians in the crosswalk.
- Yield to motorists already in the
roundabout, then merge into traffic flow when it is safe.
- Stay in your lane - never change lanes or
pass in the roundabout.
- Do not stop or pass in a roundabout.
- Signal your turn and yield to pedestrians in the crosswalk
when exiting the roundabout.
Cyclists can either ride with traffic inside the roundabout or
circulate as a pedestrian, using the sidewalk. Always yield to
Riding with traffic:
- Assert position and take center of the lane as you approach.
- Follow the same rules as vehicles and yield as you enter the
Circulating as a pedestrian:
- Most roundabouts have special ramps that lead to sidewalks.
- Dismount and walk your bike when using crosswalks.
- Cross only at crosswalks and always stay on
the designated walkways.
- Pedestrian islands may allow you to cross one section at a
- Watch for cars entering and leaving the roundabout. You
have the right-of-way, but proceed carefully.
- Your best protection is awareness.
- Never cross to the center island.
KEEP IT CLEAR
If an emergency vehicle approaches, exit the roundabout
immediately and then pull over. Do not stop in the roundabout.
Large vehicles and roundabouts
Roundabouts are designed to accommodate large trucks, farm equipment and
emergency vehicles. The 'truck apron' is specifically designed so these
types of vehicles can drive over it and make their way safely through the
intersection. Watch the video below to learn more (video courtesy of the
Federal Highway Administration, Modern Roundabouts: A Safer Choice).
ACHD and roundabouts
here to learn
more about ACHD's Countywide Roundabout Preservation Plan
Learn how the new roundabout at 36th, Hill, and
Catalpa will work by watching the
Learn more about roundabouts at these
* Statistics from the National Cooperative Highway Research Program
(NCHRP), Report 672