Have you heard of Linndale, Ohio? From Wiki:
Linndale, often called a speed trap,[6][10] had for many years the busiest, on a per-capita basis, Mayor's Court in the State of Ohio.[11][12] The village in the past has successfully defended its legal right to enforce the 60 mph speed limit on the 422 yards (386 m) of Interstate 71 within its jurisdiction under the "Home Rule" provisions of the state constitution.[10][13] The combination of traffic enforcement and Mayor's Court has provided 80% of Linndale's one million dollar annual budget, and underwritten its four full-time and ten part-time police officers.[14]
On December 20, 2012, Governor John Kasich signed a bill[15] into law effective March 22, 2013, which dissolved Linndale's Mayor's Court.[16] A sergeant in the Linndale police department stated that traffic cases would subsequently be handled by nearby Parma.[17]
The town didn't even have direct access to the interstate where they were enforcing the speed limit, they had to leave the city limits to get to an on ramp. An episode of This American Life covers the town's history of paying it's bills with speed trap revenue, including how they have adapted to the change in law mentioned above. It's incredible.
https://www.thisamericanlife.org/629/expect-delays/act-two