Longman Dictionary of Contemporary English
radar trap
noun
EXAMPLES FROM CORPUS
▪ And the beam can't be spotted by drivers who use radar trap detectors.
▪ I was pinched for dangerous driving last month, in a radar trap.
Wiktionary
radar trap
n. A roadside location, manned by police or similar officials, where a device that emits a radar beam is used to monitor the speeds of motor vehicles in order to apprehend motorists in violation of the speed limit.