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Over the last 25 years, roundabouts have been used across the United States to reduce crashes, traffic delays, fuel consumption, air pollution, and maintenance costs.
Roundabouts are specifically designed for urban, suburban, and rural locations to accommodate various vehicle types.
Traditional Intersection to Single-lane Roundabout Intersection
Back to topHow Roundabouts Work
At a roundabout, entering traffic slows down, looks for pedestrians at the crosswalk, and yields to circulating traffic from the left. Once in the roundabout, drivers follow the circle to the right (counterclockwise direction) until reaching their exit.
Most roundabouts in Iowa are single-lane roundabouts. Some roundabouts are on multilane divided roadways. See below for instructions that summarize both types.
List items for Roundabout Types
- Slow Down.
- Look for and Yield to Pedestrians at crosswalks.
- Yield if necessary to vehicles in the roundabout.
- Enter the roundabout and travel to the right until your exit.
Safe Roundabout Practices
Large Vehicles (A) - Large vehicles can use the truck apron - the dark gray colored, raised center island - for extra room for their rear wheels when turning.
Pedestrians (B) - Pedestrians should cross one direction of traffic at a time.
- At the crosswalk, look left for traffic before entering the roundabout.
- At the raised splitter island, stop and look right, then finish crossing.
If you have already entered the roundabout, continue to your exit, then pull over and allow emergency vehicles to pass.
When there are multiple lanes on at least one intersection approach, they are called multilane roundabouts.
Depending on the road you are approaching the intersection on, the additional step will be to determine which lane to be in before you enter the roundabout. Then, follow the signs and lane markings to complete your movement. Common examples are:
- a right-turn lane,
- two lanes on the main road, with one as a shared through/left-turn lane and one as shared through/right-turn lane (sometimes called a 2x1 roundabout)
- This example is like a “normal” multilane intersection – you would not turn left from the right lane, or right from the left lane. And both major road lanes go through.
In general, the steps are the same as single lane roundabouts, with an additional step to choose your lane before the intersection.
- Slow Down.
- Choose a lane before entering the intersection. Follow signs and pavement markings.
- Look for and yield to Pedestrians at crosswalks.
- Yield if necessary to vehicles in the roundabout.
- Enter the roundabout and travel to the right until your exit.
Safe Roundabout Practices:
A - Truck Apron - Large vehicles can use raised center island and curbs for extra room when turning.
B - Crosswalk - Pedestrians should cross one direction of traffic at a time; drivers should check for them when entering/exiting where crosswalks exist.
Why Roundabouts Work
Conflict points are locations where vehicle paths cross. Roundabouts reduce the number of conflict points, and especially remove the most dangerous kind of conflict points: left-turn conflict points.
In addition, since roundabouts affect the speed and approach angles entering vehicles, when crashes do occur, they are typically less severe than a two-way stop intersection or a signalized intersection.
Typical Intersection – 32 conflict points | Single Lane Roundabout – 8 conflict points |
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Roundabouts are often the most efficient alternative. The Yield control creates gaps for traffic to enter and reduces wait times compared to a two-way stop intersection and reduces stops during busy (and especially less busy) times compared to an all-way stop intersection or a traffic signal.
Roundabouts are designed for various vehicle types. Roundabout lane widths are wider than normal lanes, and these lanes accommodate cars, buses, and most small trucks that are turning or traveling straight through, as well as large trucks traveling straight through. Larger turning vehicles have a mountable central island (truck apron) and sometimes additional mountable areas on the corners, for off-tracking wheels.
Roundabouts are often constructed near schools. This is due to typical school “peak” traffic periods in the morning and afternoon, as well as the ability for roundabouts to simplify pedestrian crossings of one direction at a time. A variety of roundabouts have been constructed near schools in Iowa, including these examples:
| City/County | School District | Schools | Map Link |
|---|---|---|---|
| Cedar Rapids – Linn County | College CSD (Prairie HS) | Complex serves 6 schools (Pre-K through HS), a bus barn, and sports complex | Google Maps |
Gilbert – Story County | Gilbert CSD | Between Intermediate, Middle, and High School. Connects City and Co-op to US 69 | Google Maps |
| Fayette County | Starmont CSD | Rural intersection near combined Elementary, Middle, and High School | Google Maps |
Johnston – Polk County | Johnston CSD | Suburban High School campus | Google Maps |
| Orange City – Sioux County | MOC-Floyd Valley CSD | Urban/Rural transition of medium sized city. New Elementary to south, HS and college to west. | |
Waukee – Dallas County | Waukee CSD | Suburban. Between Waukee MS and Waukee HS. Serves Bus entrances. | Google Maps |
Design and Traffic Safety Programs and Contacts
Complimentary Roundabout Design Review Service
The Iowa Department of Transportation offers no-cost, expert roundabout reviews during the feasibility, planning, design or operation of roundabouts in Iowa. The DOT is presently using two nationally-known and respected roundabout consulting firms to help ensure early success for roundabouts in Iowa. See the Complimentary Roundabout Design Review Service brochure.
Traffic Engineering Assistance Program (TEAP)
The Complimentary Roundabout Design Review Service is funded through the Iowa DOT Traffic Engineering Assistance Program (TEAP). Cities and Counties can also apply for general TEAP studies for a range of existing traffic and safety issues. TEAP studies identify cost-effective traffic safety and operational improvements as well as potential funding sources to implement the recommendations. Learn more about the Iowa DOT Traffic Engineering Assistance Program (TEAP).
Traffic Safety Improvement Program (TSIP)
The Iowa DOT Traffic Safety Improvement Program (TSIP) provides up to 500,000 for site-specific safety improvement projects based on competitive benefit/cost evaluation. Applications are due August 15. Learn more about the Iowa DOT Traffic Safety Improvement Program (TSIP).
Iowa DOT's Traffic and Safety Bureau
Iowa DOT's Design Bureau
- Iowa DOT District Staff (Engineering and Planning Contacts)
- Iowa DOT Local System Bureau Contacts
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