Originally Posted by FBinNY

I don't know if I feel more vulnerable one way or the other, but a major difference between bicycles and motorcycles on the road relates to speed. Motorcycles move at the same (roughly) speed as cars and so are part of the laminar flow. OTOH bicycles move at between 1/4 and half the speed of traffic and so are constantly being passed. That means on a trip of any length, bicyclists will be passed by many more cars than motorcyclists. Each of those passes represents an accident opportunity, or a chance of meeting a jerk. If 1 out of 100 drivers are jerks, and you're passed by 200 drivers an hour, that's 2 jerks (on average) per hour.