Yes, speed traps are legal. They deter speeding in problem traffic areas. While many people consider a speed trap to be a form of entrapment, so long as the police conduct the traffic stop in the same way as with any other stop, they are legal. That having been said, there are still legal defenses that an attorney could use to help fight a speeding ticket. Here is a link to a site that will provide further information: https://law.freeadvice.com/general_practice/traffic_law/speed-trap-traffic.htm