I talked to a cop about how they chase bikes. He said their policy is to back off and give them room. They won't chase them hard, but they will try to keep sight of them. He they will most likely wreck all by themselves and that's when they get them. I asked him what he thought about the whole cop-car-used-as-a-road-block-to-stop-a-speeding-bike thing and he said it sounded very dangerous both for the officer and especially for the rider. He said it sounded like the officer either wasn't paying any attention, or did it intentionally, either one would a bad thing for the police department.