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What Is A Roundabout

What is a Roundabout?

A modern roundabout is a circular intersection where traffic flows in one direction, counter-clockwise, around a central circular island. It is used as a form of intersection control, like traffic signals or stop signs.

Studies by the Federal Highway Administration have found that roundabouts can increase traffic capacity by 30 percent to 50 percent compared to traditional intersections.

Modern roundabouts are designed to accommodate vehicles of all sizes, including emergency vehicles, buses, and truck and trailer combinations. In a modern roundabout, drivers enter the intersection by navigating a gentle curve, yield at entry to traffic already in the roundabout, proceed into the intersection and exit at their desired street.

A main feature of the modern roundabout is a raised center island. The circular shape is designed to control the direction of traffic and reduce speeds to 15 to 20 mph. It also reduces the likelihood of t-bone or head-on collisions.

The center island of many roundabouts includes a truck apron or raised section of concrete that acts as an extra lane for large vehicles. The back wheels of the oversize vehicle can ride up on the truck apron so the truck can easily complete the turn, while the raised portion of concrete discourages use by smaller vehicles.

In addition to the center island, roundabouts also feature triangular splitter islands designed to slow and direct traffic. The islands also provide a refuge for pedestrians. This means pedestrians can choose to cross one direction of traffic at a time and have a safe place to wait before crossing another direction of traffic.

   

Principals of a Roundabout

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