The National Speed Trap Exchange site depends on the input of drivers to find out where the cops hide. The listing is by state and than by city, so it is easy to find out where you need to watch out and hopefully avoid a ticket. Also listed are the providences in Canada as well. On the web site its states that:
The main premise of the National Motorists Association is that if motorists will join together in one organization to represent their rights and interests as drivers, they will no longer be ignored and exploited by federal, state and local.
I did a check where I live and the information is accurate. The cops in our town, like most small hamlets, need a way to generate revenue for the town.