As i understand it, there&#x27;s a rule that requires a member of staff on any train that&#x27;s properly underground. Ostensibly for safety in emergencies, but possibly because the unions fancied the jobs.<p>On current tube and big railway trains, that member of staff is the driver. On the DLR, it&#x27;s the train captain. On an automated Crossrail train, it could be a guard (it&#x27;s buses that have conductors!).