Speed Bump British English a speed or road hump, sometimes colloquially a sleeping policeman is a traffic calming tool designed to slow traffic. A Speed Bump is a bump in a roadway that may be circular, parabolic, or sinusoidal, and it may have gaps near the curb to allow drainage. The speed at which a vehicle can safely pass a bump decreases with the bump's slope. Speed Bump heights range from as little as 2 inches to as much as 6 inches, and they can vary in length from less than 1 foot (30cm) to as much as 10 feet (3m). Speed Bumps longer than 10 feet are usually called speed humps, and they are often used to slow traffic in residential neighborhoods.
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The use of Speed Bumps is widespread around the world, and they are most commonly found where prevailing vehicle speeds are expected to be low.
Although Speed Bumps are very effective in keeping vehicle speed down, their use is sometimes controversial as they can cause noise and possibly vehicle damage if taken at too great a speed. Poorly designed Speed Bumps often found in private car parks (too tall, too sharp an angle for the expected speed) can be hard to negotiate in vehicles with low ground clearance, such as sports cars, even at very slow speeds.