Somebody probably opened the wrong side once and a passenger fell out and sued... We'll see more positive train control as the technology gets cheaper: http:/

Somebody probably opened the wrong side once and a passenger fell out and sued... We'll see more positive train control as the technology gets cheaper: http://en.wikipedia.org/wiki/Positive_train_control http://en.wikipedia.org/wiki/Positive_train_control It doesn't replace operators, but instead enforces speed limits and stops. It hasn't been implemented in more trains mostly because it's expensive.