Theory 12/The rival is a different mechanism/Road safety
Variance or Mean Speed?
The claim
Fatalities track speed variance more than mean speed.
01The rival explanation
Faster roads are both more variable and more fatal, so variance is a proxy for the mean.
02What would tell them apart
Roads can be found with equal mean speeds and different variances, through limits, enforcement and mix.
03Prediction
Fatalities should differ across matched-mean roads.
04Refutation
If matched-mean roads show equal fatality rates, the rival wins.