Theory 17/Existing data/Road safety
Fatalities Track Speed Variance
The claim
Road fatality rates track the variance of vehicle speeds more than the mean speed, because variance creates the interactions that kill.
01Mechanism
Collision risk depends on relative speed; a uniform fast flow can be safer than a mixed one.
02Prediction
Fatalities should track variance at equal mean speed.
03Refutation
Fatalities tracking mean speed would remove the variance.