Being a bus driver in London is one of the worst jobs in the world if you ask me.
I asked a driver about this question and he gave me loads or reasons many of which have been covered, he did say that since the open back bus has gone drivers are far more reluctant to do it, also opening the doors disengages the drive of the bus and sometimes you have to reset them before you can drive away.
I don’t really understand how that would make a difference myself as the bus doesn’t know if it is a stop or some lights, but all the other reasons he gave seemed reasonable.
I asked a driver about this question and he gave me loads or reasons many of which have been covered, he did say that since the open back bus has gone drivers are far more reluctant to do it, also opening the doors disengages the drive of the bus and sometimes you have to reset them before you can drive away.
I don’t really understand how that would make a difference myself as the bus doesn’t know if it is a stop or some lights, but all the other reasons he gave seemed reasonable.
Guilty m'lord on a tube breakdown day when I'd waiting 45 mins for a bus (any bus) to take me somewhere and none of them would open their on doors, just the off ones. 

