Roundabouts

A roundabout is a circular intersection that uses geometric features to slow traffic and safely direct vehicles in multiple directions. A roundabout consists of a circular roadway that wraps around a central island, and this physical configuration forces drivers to reduce speed during the approach, entry, and movement within the roundabout.

The design of the roundabout depends on the road’s specifications. The general rule of thumb is that roundabouts with large central islands (150-200 feet in diameter) are best suited for roads with a high traffic volume and speed limit. Smaller roundabouts (50-100 feet) are best suited for residential areas with a low traffic flow and speed limit.

Generally, roundabouts are safer than traditional intersections. Studies have shown that roundabouts have 40% fewer vehicle collisions, 80% fewer injuries and 90% fewer serious injuries and fatalities. Roundabouts are also preferred by some traffic engineers because they often have shorter delays and queues than intersections with traffic lights.

The first modern roundabout was constructed in Paris around the Arc de Triomphe in 1901, and the first one in the US was Columbus Circle which was built in New York City in 1904.

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  1. Andreas Broscheid

    Do the accident data that you cite distinguish accidents involving pedestrians? I always found roundabouts a major pitn to cross on foot, but maybe this perception is wrong.

    One argument for roundabouts is obviously the reference in the Hitch Hiker’s Guide to a Basingstoke roundabout…




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