Did He Thank Me?

I was driving to work this morning, and a black pick-up truck came speeding up behind me. It wasn't super-fast, and he never got super-close, but he was definitely going several miles per hour above the speed limit. My guess is that he was probably annoyed (although I didn't see the tell-tale signs of hand waving or other gesturing), but I wonder if he was thanking me when we got to the speed trap. Chances were pretty good that he would have gotten a ticket if he didn't come up behind me and was able to continue at the speed he was going.