Several little towns in Nevada that have speed limits a long ways from their civilizations. Searchlight, NV is one. Don't think they use cameras though. Patrol vehicle or vehicles are on duty and they justify their prescence. 
Waze app on your smart phone can give warning of some of these things but phone screen can be hard to read sometimes. Latest OTA update for the nav screen on my Tesla, now shows traffic cams, traffic signals, speed traps, wrecks and congestion so you know what's ahead. Construction zone speed limits can be tricky for older GPS systems because the posted limits, according to the GPS are usually fixed from the last time the road was surveyed. Tesla's vision based driving assistance reads signs as you pass them and post speed limit on your nav screen, along with a warning chime to alert you of excessive speed.