They shot your front tag? So this happened in a car? Was trying to understand how the traffic camera got a bike, since they usually take picture as you approach.
I have a simple rule, when I'm on a highway and enter towns I slow down, even without or before seeing a speed limit. Traffic, pedestrians, kids, pets all those hazards are a good reason to slow. I'm more likely to accelerate too soon leaving town, that's the last time I was pulled over (let off with a warning) for speeding. Still I've seen some of these speed traps and know how easy it can be to miss the sign, or not have enough time to slow.
