Driving on Rt. 28 north towards Frederick, MD, a black BMW 325i is on my ass! I have a slower car in front of me. Not sure what the asshole thinks I can do, I can't drive any faster with a car in front of me. He keeps riding up on my bumper. At a passing zone right after Rt. 109 near Poolsville, I pass the car in front of me with authority to try and lose this idiot. He passes the car also and once again tries to ride up on my ass. I am now traveling over 100 and this guy just won't leave me alone. I slow down and he passes me with an oncoming car going southbound , almost in a head on collision! What an ass! He turned north on Rt 464 towards Jefferson. This guy has serious issues!