I ran in college and that's when all the runners were able to do a 10 mile run at 6 minute mile pace. I can't imagine doing that now. Cross country race pace was even faster. I really enjoyed it but now with the extra weight that I carry, it started to hurt my knees. Even when I dropped my weight, it still hurts. Thank goodness for bike riding.

as far as bike accidents with cars, I am lucky to be in So Calif and near the Santa Ana River Trail, the San Gabriel River Trail and the Los Angeles and Rio Hondo River Trails. Those 4 asphalt trails give a rider plenty of endurance workouts with no cars.