Had a good friend get a rear flat on his bike. He said bike wanted to just go straight. Only brake you have when tire breaks bead from rim is the front or shoes as Toby pointed out. Also took 3 of us to push bike onto his trailer.
Ouch! Got me there! HEHEHE It did finally hit me to check on you though. LOLIf your back tire is flat, you don't have to worry about stopping. It will stop on it's own. The bike barely rolls!
You will however have to worry about your friends stopping