FHWA Resource Center
SAFETY AND DESIGN TEAM
Illustrative background photo of entrance lane of a roundabout featuring MUTCD diamond shaped, yellow roundabout sign. Car traveling through roundabout and center island landscaping is visible.
Your community deserves a lot less...
Illustrative background photo of landscaped roundabout
...less congestion, less frustration, fewer traffic collisions, less pollution, less expense
Roundabouts: the more you build, the less you get.
Left-hand inside panel:
What is a roundabout?
A roundabout is a one-way, circular intersection without traffic signal equipment in which traffic flows around a center island.
Illustration of features of a typical roundabout view from above with prominent features identified. Caption reads "Illustration of the features of a roundabout."
Through proper design, roundabouts can easily accommodate emergency and large sized vehicles. Drivers should behave in the same manner as they would on any other road if an emergency vehicle approaches: carefully move your vehicle as far right as possible and, if necessary, stop until the emergency vehicle passes.
Illustration: Drawing of the potential conflict points in a roundabout versus a signalized intersection for comparison purposes. Caption reads "Signalized intersection: 32 conflict points, Roundabout: 8 conflict points."
Center inside panel
All Roundabouts have these features
Traffic entering the circle yields to traffic already in the circle.
- Traffic Deflection
Pavement markings and raised islands direct traffic into a one-way counterclockwise flow.
- Geometric Curvature
The radius of the circular road and the angles of entry can be designed to slow the speed of vehicles.
Illustration: Drawing of a roundabout using arrows to indicate the driving path taken through a roundabout when a driver does not wish to make a turn. Caption reads "Driving straight through a roundabout".
Illustration: Drawing of a roundabout using an arrow to indicate the driving path taken through a roundabout when a driver makes a left-hand turn. Caption reads "Left-hand turn."
Because the only movement allowed upon entry or exit from a roundabout is a right turn, the occurrence of crashes that result in injury is substantially reduced. Small-angle collisions, the type of collisions that can occur as a result of a right-hand turn, are typically less severe than other types of collisions.
Roundabouts save lives.
Right-hand inside panel
Benefits of a roundabout:
- Up to a 90% reduction in fatalities
- 76% reduction in injury crashes
- 30-40% reduction in pedestrian crashes
- 75% fewer conflict points than four way intersections
Slower vehicle speeds (under 30 mph)
- Drivers have more time to judge and react to other cars or pedestrians
- Advantageous to older and novice drivers.
- Reduces the severity of accidents
- Keeps pedestrians safer
Efficient traffic flow
- 30-50% increase in traffic capacity
- Reduction in pollution and fuel use
- Improved traffic flow for intersections that handle a high number of left-turns
- Reduces the need for storage lanes
- No signal equipment to install and repair
- Savings estimated at an average of $5,000 per year in electricity and maintenance costs
- Service life of a roundabout is 25 years (vs. the 10-year service life of signal equipment)
- Traffic calming
- Aesthetic landscaping
Illustration of a roundabout superimposed with arrows indicating the path of traffic around the center island in a counterclockwise direction. Caption reads "Continuous counterclockwise traffic flow"
Back center panel
Education is vital to the success of a roundabout! Navigating a roundabout is easy. But because people can be apprehensive about new things, it's important to educate your community about roundabout use. There are just a few simple guidelines to remember:
1) Slow down.
2) Yield to traffic already in the circle.
3) Obey one-way signs at all times.
4) Watch for pedestrians and bicycles throughout. Left turns are completed by circling around the center island and then making a right turn to exit from the roundabout.
Roundabouts have been used successfully all over the world, including in Australia, Western Europe, The Czech Republic, Israel, and Canada. In the U.S., communities in Kansas, Colorado, and California, Florida, Maryland, Vermont and other states are currently using roundabouts successfully. Roundabouts are not suitable for every intersection. Please consult Roundabouts: An Informational Guide for more information.