Male driver rides up on your bumper and flashes lights at you (I say you because he did it to me and then I witnessed him do it to another car when exiting highway). I was in the fast lane and already speeding; he came up behind me. There were cars in the lane beside me and I could not move over for him. As I mentioned, I was already speeding. He rode my bumper and then started flashing lights on and off, and I could not get over. When an opportunity to get over came up, it would put me behind a slow-moving truck, which I didn't want to slow down for, so I waited to pass the truck, which seemed to infuriate the driver. I got over after passing the slower-moving truck, and this driver got over with me and followed closely behind me, no longer in such a hurry. He continued to follow closely behind me, then passed me. I looked over at him, but he did not look at me. Then he got in front of me, slowing down to below the speed limit. I changed lanes to go around him, but he changed lanes in front of me, as if to not let me pass. Guessing he noticed he was being filmed, at which point he sped off. He exited the highway, and I witnessed him speeding up and braking quickly for a car on the exit ramp. He also rode that car's bumper down the exit ramp.