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# Circumference

## Pi times the diameter or the distance around the circle.

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A Roundabout Way Home

How can the circumference of a circle make drivers safer? When it’s part of a roundabout! Roundabouts can replace four-way intersections. They improve traffic flow and safety, especially in urban areas.

#### How to Drive on a Circle

Modern roundabouts should be navigated on the basis of the “yield-on-entrance” rule. This means that when you arrive at the roundabout, you must wait for a break in traffic to enter the circle. In some circles, different lanes lead to different exits. Motorists drive around the circle at about 25 miles per hour until they reach their exit.

Urban planners choose to use roundabouts because they’re less congested and safer than typical intersections. In a roundabout, a “T-bone” collision (depicted above), the most dangerous type of auto accident, is impossible. Because cars are driving slowly and at a constant pace, the flow of traffic is predictable. Some experts claim that replacing traditional intersections with roundabouts would reduce injuries from accidents by 80%.

See for yourself: http://www.youtube.com/watch?v=X0RcTWEBtYM

#### Explore More

Roundabouts are becoming more common across the United States. Learn how to drive them, so you won’t be surprised when you encounter one.

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