Here's a cross post from the jogger injured. Feel free to check my formula/math if you like.


As for speed limits. You'll still have to catch and ticket the people going too fast. You can't and won't catch them all. Even then, say a 15mph speed limit is enough to kill or seriously injure someone if they land on their head the right way. How fast was this cyclist going? Does anyone have any ideas?

Lets play a math game. Formula: F = m Dv/Dt Where F = force, M=mass, Dv=delta velocity, Dt= delta time. A quick google search gives me .0455 as a unit conversion for pound-miles per hour per second.

Say, a 200lb cyclist (180+ bike) traveling at 15mph hits a jogger who is stopped. Lets say it takes .5 seconds to 'stop' motion completely, since the jogger will give a little when hit. That's 200*15/.5 *.0455= 273lbs of force applied instantly to someone's shoulders. I'm too lazy to calculate the falling velocity of the runner when they actually are accelerated from 0 to whatever speed when they hit. I suspect it's in the neighborhood of 200lbs of force directly to the head when they impact.

Given the impact is more along the lines of .2 seconds and not .5, that force will nearly triple.

Lets do something else: A runner doing speed work. 6min mile isn't too hard for someone 'fit'. I'm not much of a runner and can run a sub 6min mile. I weigh 190lbs dressed. Lets assume it takes .3 seconds for us to crash and stop.

so 190*10/.3=6333.3...(.0455) That's 288lbs of force. More force than my first example, and with the right bad circumstances, enough to kill someone.