Manufacturers are known to bribe municipalities and take a cut of the generated revenue as well.
https://www.illinoispolicy.org/after-1b-in-tickets-and-4-corruption-indictments-illinois-should-shutter-the-red-light-camera-industry/
https://www.illinoispolicy.org/after-1b-in-tickets-and-4-corruption-indictments-illinois-should-shutter-the-red-light-camera-industry/