Isn't it exactly the opposite of how you describe it? > That's really why "miles" is a poor measure. It implies going faster is safer. A mile is a mile no mat

Isn't it exactly the opposite of how you describe it? > That's really why "miles" is a poor measure. It implies going faster is safer. A mile is a mile no matter how fast you drive. It means that in a 13mi trip statistically you will have to intervene once regardless of the speed. > It would be better to list intervention per hour And this means that if you have a 13mi trip you'll just floor it to reduce the time, and thus the number of interventions per time (hour). I agree with mentioning road type and other conditions, like weather. You want to know if the system is significantly worse in snow or fog.