A speed camera lottery has been working well in Stockholm, Sweden. Drive at or under the speed limit and you'll be entered into a lottery where the prize fund comes from the fines that speeders pay. Average speed reduced from 32 km/h to 25 km/h (a reduction of 22%).
The lottery is the result of an ideas competition run by Volkswagen.
https://www.wired.com/2010/12/swedish-speed-camera-pays-drivers-to-slow-down/amp