Roundabouts

Rules of the Roundabout

  • Slow down when approaching a roundabout.
  • Choose your lane upon entering the roundabout based on your desired exit or destination.
  • The right lane is for straight-through movements or right turns.
  • The left lane is for straight-through movements, left turns or U-turns.
  • Yield. All entering vehicles must yield to circulating traffic in the roundabout. Look to the left for circulating traffic and enter when it is safe.
  • Do not change lanes. Maintain your lane position until exiting the roundabout.

Driving Modern Roundabouts

Research shows that drivers quickly adapt to the roundabout traffic flow. Proper use of signing and road striping at roundabouts assists motorists and minimizes the potential for confusion.

Community gateways and main streets are effective locations for roundabouts as they slow traffic and provide space for an aesthetically pleasing entrance treatment. In addition to the beauty they can provide if landscaped well, roundabouts slow traffic and help pedestrians cross the street.

Roundabout Safety

Roundabouts limit vehicle speeds to approximately 20 miles per hour (mph) and can control vehicle flows on 4 streets simultaneously. Compared to traffic signals, roundabouts typically reduce crashes by 40 - 60%, reduce injury by 35 - 80%, and almost completely eliminate incapacitating injury and fatal crashes.

Statistics

There are 2 basic premises in which roundabouts achieve this. The 1st is the simple decision making and the 2nd is the low level of conflicts. At a 4-way intersection there are 32 possible conflict points between vehicles and only 8 at roundabouts. Pedestrians face 6 conflict points when crossing only 1 leg of the road at a 4-way intersection; at a roundabout, they only have 2.

A diagram of merging points on a 4 way intersection
A diagram of merging points on a roundabout

Modern Roundabouts vs. Traffic Circles

There are many differences between roundabouts and traffic circles.

  • Unlike traffic circles, roundabouts are used on higher volume streets to allocate right-of-way between competing intersection movements.
  • Traffic circles have a large diameter, which contributes to high circulating speeds; roundabouts have a smaller diameter, promoting low circulating speeds.
  • Roundabouts have lower entry speeds compared to traffic circles and feature a yield at every entry point, promoting low speed and no weaving.