As a bit of a side note, I just want to remind all of you of how the stopping distance is related to v^2 , so don't get fooled into thinking that if you go twice as fast it'll just take twice the distance to stop. That's wrong. If you're going fast enough, that estimation will be off by quite a bit. The same goes for the 2 second rule for traveling behind cars. If you're going fast enough, the rule isn't that effective. Not to mention, at higher speeds, the friction from your tires decreases.