At 15+ MPH, MUPS get downright dangerous. The pylons they put up at every intersection to prevent cars (i guess) from getting in become dodge hazards. Not to mention that at every block it puts you in a crosswalk. Not to mention that at those crosswalks, cars aren't looking down the MUP to see if any 20 MPH vehicles are coming at them. Not to mention that the average walker freaks out when you alert them, usually diving in your way by accident instead of away from you.