ROUNDABOUT DESIGN

Roundabouts are designed so that drivers slow down before entering and then maintain a slow, consistent speed through the intersection.   Here are some of the design features typically found at a roundabout and how they contribute to the roundabout’s safety benefits.


Counter-clockwise circulation.  Drivers are directed into this pattern, nearly eliminating the chances of right-angle collisions since vehicles are moving in the same direction.

Circulatory roadway. The radius (tightness of the circle) of the roundabout is designed so motorists drive at a consistent, slow speed around the center island.  The number of lanes depends on the volume and types of traffic that are expected at the intersection.

Splitter island.  The splitter islands separate the entering traffic from the exiting traffic.  They guide drivers in the proper direction for entering the roundabout and driving in a counter-clockwise circulation.

Truck apron. A truck apron with a low curb is used when the types of vehicles expected at the intersection include large trucks that make wide turns.  The apron allows trucks to roll their rear wheels over the low curb as they move through the roundabout.  The low curb discourages other drivers from using the apron, helping to keep their speeds slow and consistent.

Accessible pedestrian crossing.  Not all roundabouts have this feature because pedestrians aren’t allowed or encouraged in situations such as high traffic volumes.  Where allowed, pedestrians shouldn’t cross the middle of the roundabout.  Instead, they should use the crosswalks through the splitter islands where they can pause, if needed, before crossing the far lane of traffic.

Entrance line.  The entrance line indicates where drivers should wait when yielding to approaching vehicles already in the roundabout.

Central island.  The central island is the reference point for driving counter-clockwise in a slow, consistent speed through the roundabout.  In some situations, local governments landscape the island or add public art, making an attractive addition to the area.

urban roudabout

Seven design features of roundabouts

 

 

typical collision

Roundabout near school and business

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