Actually, riding a bicycle with a radio or speakers on the front or rear rack would be closest to driving in a automobile while listening to the radio and driving with headphones would be more like riding a bicycle with headphones. As for the primary differences between a bicycle and automobile...hmmm...let see...I guess they begin with the hierarchy on the road. Further differences include the physical properties of weight/momentum/width/length, number of wheels and tire width, bumpers, doors, hood, roof, windshield, seatbelt, airbag, heat, glove compartment, horn, brake lights, directional lights, air freshener, rear and side view mirrors, . One similarity may be that hybrids can be as silent and both fixed gears and cars can go in reverse. If riders need music to motivate them or help pass the time, perhaps they should listen to music on a stationary bicycle or on the bus. Headphones don't only compromise the offenders standing on the road, but mine when they don't hear me coming or passing. I would suggest that most accidents occur with non-emergency vehicles. Being aware on the road extends beyond hearing emergency vehicles and crying babies. Try watching television with headphones and hearing a knock on the door.

However, listening to healthy NPR programming does indeed absolves rider responsibility and provides a divine cushion (it says so on their website). Carelessness, collisions and not being aware what or who is behind you is reserved for those with Smashmouth, Olivia Newton John and Deicide in their shuffle.