A speed trap
is a location in which the posted speed limits are
not easily seen thereby making it possible for the police to write
traffic tickets. Speed traps often are found in small towns, often near major highways, in which
travellers are unlikely to return to challenge a speeding ticket.
Some communities with reputations as speed traps have a disproportionately large number of their local workforce involved in law enforcement or judiciary occupations.
In some small towns and counties, traffic fines make up a large
fraction of the income of the local government, which gives the
police an incentive to write tickets. In the state of Texas
this conflict of interest was severe enough so that the state
legislature passed a law limiting the fraction of revenue that
a local government could derive from traffic tickets.