There ARE 30 mph speed limit signs if a driver is observant like they should be. But the cops cheat anyway....wife got a ticket of 47 in a 30 from a cop car moving in the opposite direction. When she asked how he could get a radar reading when they were on a curve, he said "I can move my radar gun to the side". He completely screwed up the proper usage of the radar and I wanted to fight him in court but the wife was intimidated by the "plea" down letter she received. Tix was $75 and 2 points for "Defective equipment". The plea letter was very threatening stating going to court could cost up to $250...so she wouldn't let me help her. I would have sat that cop back on his ass by having him explain how he could move his gun from straight ahead to an angle off, which results in a PANNING ERROR. Moving a radar gun like that has shown stop signs traveling 75 mph!!. Then there is the COSINE ERROR in which any angle off from straight results in an error, thus if a cop on an interestate going the opposite direction catches a speeder, the speeder will usually just pay because the angle off from straight shows the speeder SLOWER than he actually was traveling, so they think they got away with something..which they did. BUT, if the cop moves the radar off to the side from straight ahead, then it results in the computer thinking the cop car is moving SLOWER than it is, so results in the TARGET SPEED READING faster than the target is moving. I got a copy of the notes on the ticket the cops always write when they are thru with the speeder, and it showed the first contact at 20 ft. then showed that she had slowed down to 45 and then 40. I'd have busted him again because at 47 mph one is traveling at prox 67 feet per second, so she would have been past him in 1/3 of a second, no way to show 47, 45 and 40. The cop LIED and CHEATED. I was a Radar Intercept officer in Navy F-4's and trained in dopplar and pulse radar operations and possible/probable errors that can happen with improper use.