Well by law, you should be slowed down to the posted speed before you pass that sign up. Sounds like the cop was just trying to be a dick. I got a similar ticket, actually mine was the same ****ing thing. Just pulled out of my house, and on to the main road to take the girl home about 2:30. Come down a hill, doing 53 in a 45 which imed. dropped to a 30. (Speed trap) Well that cop being bored as **** clocked me right as I passed it or she says, I went to court and she never even showed up. Ticket got dropped.