Discription of Events: The truck was in front of me on the highway. He moved into the right lane allowing me to pass him. Just as I got past him he moved back into the left lane behind me. He got so close to my car I thought he hit me. Then he backed off and sped up again. He was so close to my bumper I couldn't see his license plate. All I could see was his grill on the front of his truck. He did a third time and I moved over to the right lane to let him pass and he flipped me off as he passed me. I wrote his license plate number down as he passed me doing 80 mph in a 60 mph zone.