15 mph isn't bad. I've gone faster than that in remote unpopulated areas but mostly 15 mph is fast enough. I'm faster on the roads. we had a death on a popular paved trail this spring. that was pretty sad. 2 guys riding in opposite directions collided. a little law/speed enforcement wouldn't hurt that trail in the busy parts. cpl years ago I saw an elderly woman on the ground dazed & surrounded by ppl including one cyclist. I'm guessing he knocked her over. ppl don't like law enforcement, but I think they like injured or dead relatives even less