Originally Posted by
njkayaker
And it's even worse using risk-per-mile because most people (we are talking about populations) will travel fewer miles when they choose to ride over driving because they mostly don't have the time to ride as many miles as they can travel driving.
Per mile is the best way to calculate risk for commuting.
For pleasure riding or riding for exercise, you'll want to go with time spent doing the activity.
Assuming you're trying to zero in on your personal risk.