I do sometimes tap cars on the roof or window if the drivers disregards my rights in a dangerous way. Today I was (in the darkness with my headlamp) going to work riding downhill. On my left a smaller road exits into my road and from that road a van is coming. I have right of way but he just keeps coming so I have to brake in order not to crash. I get angry, there is no one coming in the opposite direction so I pass him and taps his window with my gloved hand. He roars the engine and follows me in a left turn down a oneway street. 50 feet down the street he just rams into me from behind with no warning. I summersaults over the bike and it hurts quite a bit. I approach the car yelling about what the heck he thinks he is doing. He swings at me and wants to start a fight. Some other people gather and he claims not to have seen me. Then he angrily accuses me of riding my bicycle as if I were a car. I do not have my wits about me so I do not get the names of any of the witnesses. He hands me his card and says he doesn't care if I press charges. Probably won't do any good(my word against his) but I have an appointment tomorrow morning with the police and will report him. Lesson for me: Never challenge something that weighs 25 times your own weight, I really want to be around to see my childrens children (when and if they come).