sentences:  One-man operation
  
  One-man operation (OMO), also known as driver-only operation (DOO), one person operation (OPO), single person train operation (SPTO), or one-person train operation (OPTO), similarly to Driver Controlled Operation, is operation of a train, bus, or tram by the engineer or motorman alone, without a conductor.On one-man operated passenger trains, the engineer must be able to see the whole train to make sure that all the doors are safe for departure.