Bus and MAX operators have a brief window of time to board waiting passengers, close the doors and make it through a green light. In some instances, opening the door again to let you on would cause your bus or train to miss a signal — this may seem like a small inconvenience, but these delays add up quickly and can make the bus or train fall behind schedule.
By the way, we don’t advise running for any bus or train. It’s not worth the risk.