Near my parents is a Gateway National Recreation Center. They have a Multiuse Path with a speed limit of 15. That path is all but useless if you want to go for a real bike ride. I mean, not to bag on the people on it, but the people on it are barely doing 5 and have twelve kids and walk 5 abreast covering both directions.

In other words, useless.

Now don't get me wrong, I'm not the impatient jerk behind them yelling "On your left" etc. I just avoid that specially designed path altogether and ride laps on the entrance road. Much less to worry about when you're moving the same direction as traffic and, if the traffic follows the speed limit of 20, almost the same speed.