Roundabouts are a modern solution to intersection safety and capacity problems.

Better than light signals or stop signs, modern roundabouts have additional benefits that are far too numerous to ignore.

Modern roundabouts are circular intersection control devices that share the same basic function provided by light signals or stop signs. Unlike other intersection alternatives, roundabouts have fewer drawbacks and many benefits.

Benefits of Using Roundabouts

Traffic can continuously flow through the intersection, allowing higher capacity than a similarly-sized signalized intersection.

Modern Roundabouts reduce:

  • Traffic delays
  • Crash rates, particularly injury-producing and fatal accidents
  • Construction and maintenance costs
  • Fuel consumption 
  • Air pollution

And yet the modern roundabout is just now gaining popularity in the United States, after being successfully incubated in Europe, Australia, and Canada over the past few decades.

Design & Functionality

Roundabout design and functionality increase capacity and safety, and reduce delay: 

  • Traffic is always moving, as compared to signalized intersections where there is considerable dead time and start-up time. 
  • Design slows vehicles down thereby allowing tightly spaced circulating traffic, and safe and efficient weaving in multi-lane roundabouts. 
  • Design acts to slow traffic rather than enticing them to speed up to make a green light. 
  • Slow speeds and fewer possible conflicts and tangential movements create a safer intersection. 
  • Roundabouts are secondarily an effective traffic calming device since they force vehicles to reduce their speed upon approaching the intersection, thereby creating safer intersections for all users, including bicyclists and pedestrians, thereby enhancing the inter-modality capacity of a roadway. 
  • Design allows for larger left turn radii than signalized intersections and "truck aprons" so that trucks, emergency vehicles, and other large vehicles can comfortably navigate the roundabout and make left turns. 
  • Roundabout design offers superior performance at intersections with more than four legs, such as the village of Chatham on Route 41. 
  • Because traffic from each approach can simultaneously enter a roundabout, the capacity is typically higher than at stop-controlled or signalized intersections. A one-lane roundabout typically has a capacity of 2,500 to 2,800 vehicles per hour.
Roundabouts for
Route 41

The two-lane "roundabout-centered" plan for PA Route 41 could be designed, funded, and built much more quickly and at a fraction of the cost than any four-lane alternative.


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