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Roundabouts offer improved safety with fewer conflict points and slower speeds. Roundabouts also help improve motorists’ decision making while driving through the intersection. PennDOT is installing roundabouts across the state and requires that this design be considered when a significant intersection update is planned. Intersection and Interchange Geometrics, which includes roundabouts, is a Federal Highway Administration (FHWA) Every Day Counts Round 2 (EDC-2) innovation that Pennsylvania championed. 

How Does It Work?

A roundabout is a type of circular intersection that does not require vehicles to stop before entering the intersection. Roundabouts complement transportation objectives like improving safety without compromising the ability to keep people and freight moving through towns and cities. The roadway curvature encourages reduced vehicle speeds and entering traffic must yield to circulating traffic.  

The essential characteristics of all roundabouts include: 

  • Traffic travels counterclockwise around a center island 
  • Vehicles entering the roundabout yield to traffic already circulating 
  • Roundabouts result in lower vehicle speeds, generally 15-25 miles per hour 

Roundabouts and traffic circles are often confused. However, there are many differences between the two. Roundabouts are designed to be as small as practical to accommodate continuous, slow-moving traffic. Entering traffic must yield to circulating traffic. Traffic Circles vary significantly in size and traffic speeds. Entering traffic or circulating traffic may be controlled with stop signs or traffic signals. There may even be parking within the circle.

Learn more about how this innovation works on PennDOT’s Roundabout webpage.   


What Are The Benefits? 

Roundabouts are considered a safety countermeasure due to their ability to substantially reduce the types of crashes that result in injury or loss of life. They significantly reduce head-on and T-bone crashes. They also decrease congestion with the constant flow of traffic and improve pedestrian and bicycling crossing with slower moving traffic and refuge areas. Roundabouts complement other common community values with quieter operation, improved function and aesthetic options as opposed to traditional intersections.  


When comparing a roundabout to a traffic light, studies show that roundabouts provide a 90 percent reduction in fatal crashes and a 75 percent reduction in crashes with injuries. 

Innovation in Motion 

Roundabout at the intersection of U.S. Route 222 and Pennsylvania Route 662 in Richmond Township, Berks County

Education is vital to the acceptance and success of a roundabout. PennDOT District 5 designed a roundabout at the intersection of U.S. Route 222 and Pennsylvania Route 662 in Richmond Township, Berks County. The intersection is heavily used by local Amish and Old Order Mennonite communities. 

To ease their concerns, a team from PennDOT District 5 helped organize a special outreach meeting with the communities’ members. The team explained how the speed inside a roundabout of 18 to 24 miles per hour is about the same speed as a horse and buggy, so they will travel roughly the same speed as the rest of the traffic in the circle. The team also explained how a bicyclist has the option of riding through the roundabout, or they can dismount and walk through as a pedestrian. 

The $6.6 million project replaced a signalized intersection with a modern roundabout, along with widening U.S. Route 222 to four lanes at the roundabout approaches. Since its opening in May 2018, the roundabout has seen no major crashes. 

More Information

For more information about this innovation, contact the STIC Management Team.