[astrodust]

> It can be very difficult for someone to notice a bicycle on 40~55mph roads...

While people do get hit and killed on back country roads, the vast majority of collisions and fatalities are within cities where cycling on roads with that speed is ill-advised.

Most cyclists are on roads with 25-35mph speed limits. If you can't see potential hazards and react in time, you're driving too fast and should slow down. This is why there's a push for lower speed limits in urban areas: It has an almost immediate effect on collisions.

Reacting to something at 20mph and 40mph are worlds apart. You'll have no trouble stopping at 20, but at 40 you run someone over and crash into something.

[uoaei]

For some perspective, consider kinetic energy. You possess 4x as much energy travelling 40mph as 20mph.

Put another way, it takes 3x as much energy to go from 40 to 20 as it does from 20 to 0.