Do roundabouts save lives?
Intersections are among the most dangerous and complex traffic features that drivers encounter. According to National Highway Traffic Safety Administration data, 21 percent of all traffic fatalities and roughly 50 percent of serious traffic injuries can be attributed to intersections. Roundabouts almost completely eliminate fatalities and significantly reduce injury crashes.
A 2015 safety study produced by the University of Wisconsin Traffic Operations and Safety (TOPS) Lab showed that fatal and severe injury crashes decreased by 40 percent at Wisconsin roundabouts. The Insurance Institute for Highway Safety found roundabouts are safer for two main reasons:
- Less potential for serious crashes (head-on and T-bone collisions are eliminated)
- Low travel speeds (less severe crashes result from lower travel speeds)
"In typical traffic engineering, there's a tradeoff between safety and operations. Generally, 'safe' equals 'inefficient.' Our research has shown roundabouts offer benefits in both safety and operations."
David Noyce, Chair, UW-Madison
Civil and Environmental Engineering Department
Do roundabouts reduce congestion?
Roundabouts can handle more traffic in the same amount of time because traffic is not required to stop – only yield. A study measuring traffic flow at intersections before and after conversion to roundabouts in Nevada, Kansas and Maryland found that traffic delays were reduced between 13 to 23 percent.
How much do roundabouts cost?
The construction costs of roundabouts and signalized intersections are generally comparable. Actual costs depend on site specific conditions. When an intersection is completely reconstructed, the construction cost of a roundabout versus a signalized intersection is considered to be about the same.
The estimated construction cost of a single lane roundabout typically ranges from $1.2 to $1.8 million. Multi-lane roundabouts typically range from $1.8 to $2.4 million.
In some instances, roundabouts provide cost savings to the local community, developers and the department. Some examples include:
- In nine interchange/overpass locations, where roundabouts were constructed as part of the I-41 project in Green Bay, an estimated $1.7 million was saved, largely because a narrower 5-lane bridge could be built instead of 10 lanes leading to the Mason Street roundabouts.
- The five roundabouts on WIS 145 at Cabela’s Way, Richfield, were a lower cost and faster solution than intersections with traffic signals. The roundabout design required less right of way, as well as fewer lanes at the interchanges, which meant narrower bridges and on/off ramps.
- The development of Pabst Farms (County P/Sawyer Road), in Oconomowoc, required upgrading to a full interchange. The four roundabout designs allowed shorter, less costly bridges, reduced right of way, and avoided a more costly multi-lane eastbound on-ramp and acceleration lanes that would have required widening Lake Nemahbin bridges.
- On I-43 at Racine Avenue in New Berlin, the installation of roundabouts at the two interchange ramps saved approximately $1 million by eliminating the need for additional bridge width and associated lane width that would have been required for an intersection with traffic signals.
- Working jointly with the village of Saukville and developers, roundabouts were chosen in place of signalized intersections on WIS 33 east of I-43. Roundabouts fit with the developer’s plans and allowed reduced right of way and lane widths.
Are roundabouts the preferred WisDOT intersection design?
Roundabouts are not a silver bullet. Roundabouts can achieve safe and efficient traffic operation and reduce congestion when detailed technical analysis and sound engineering principles are applied to the design. In situations where minor improvements will solve the problem, signalized intersections may be more appropriate.
Does public input influence roundabout consideration?
The department believes in the importance of communicating early and frequently, especially on projects that contain features that may be new to the community. Staff meets with local officials, businesses and community members to get input early, when a transportation concern is first identified, through the design phases. Where safety concerns were not the primary factor for a roundabout project and community opinions were opposed, other intersection designs were typically selected. In some cases, communities have requested roundabouts for a particular location, but the engineering review did not support its selection.
Is public opinion on roundabouts changing?
Research has shown that the number of people who favor roundabouts more than doubles as they gain experience with them. A survey by the Insurance Institute for Highway Safety showed that before construction, the number of drivers in favor of roundabouts was only 31 percent and those strongly opposed was 41 percent. Follow-up surveys after roundabout installation showed those in favor increased to 63 percent and those strongly opposed dropped to just 15 percent.
Are there environmental benefits from roundabouts?
While cars and trucks are increasingly cleaner and greener, vehicles idling at a signalized intersection still emit pollutants and gases into the atmosphere. Stops and starts use more fuel. Because roundabouts reduce the number and duration of stops, they also reduce vehicle emissions and fuel consumption. In a study of 10 intersections in Virginia, the savings amounted to more than 200,000 gallons of fuel per year.
How does the department facilitate large vehicles travel through roundabouts?
WisDOT recognizes the importance of providing safe, efficient travel and accommodating the freight industry in delivering goods and services, as well as other large vehicles such as emergency vehicles, buses and farm equipment. WisDOT remains committed to implementing the latest roundabout technology and research with its roundabout designs. Unique roundabout design features can be implemented and have been implemented on WisDOT roundabouts to accommodate oversize/overweight trucks.
What needs to be done to decrease the fender-bender crashes occurring at roundabouts?
Despite the growing number of roundabouts across the nation, for some drivers, roundabouts are new. Safely maneuvering a roundabout requires drivers to be alert and follow three key rules:
- Slow down
- Choose the correct lane
- Yield to all lanes
Failing to follow these basic rules can increase non-injury crashes.
WisDOT provides outreach materials to local communities , including driver educators, to help motorists adjust to driving roundabouts. A video tutorial and other materials are available on
WisDOT’s website. The Division of Motor Vehicle Motorists’ Handbook includes a special section with information on how to drive in a roundabout.