sleeping policeman
n. A speed hump or speed bump.
Examples
1996
In Atlanta, Dallas, San Francisco and other cities, the speed hump, or bump, popularly known as the sleeping policeman, has been gaining in popularity.
—Garry Pierre-Pierre, “Listen: No Thump. Speed Humps Are Lower. Also Quieter, Kinder and Gentler,” The New York Times, September 02, 1996
1987
You can be 'radared' from overhead but, as in France, if there is a trap threatening, other drivers will flash a warning; though helicopters are not yet, to my knowledge used across the Channel. And you will find many warning notices of speed detection devices by the road side — something of a sleeping policeman device but worth bearing in mind.
—Roy Harry, “Backwards thinking,” The Guardian (London), October 19, 1987
1969 (earliest)
When you hear a Jamaican talk about his country's "sleeping policemen," he isn't implying that Jamaican lawmen aren't wide awake. The term "sleeping policeman" is used to describe the hump built across streets to slow down speeders,
—“Sleeping policemen,” Colorado Springs Gazette-Telegraph (Colorado Springs, Colorado), November 08, 1969
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