One-man operation (OMO), driver-only operation (DOO) or one person operation (OPO) is a method of train or bus operation in which the vehicle is operated by the motorman or driver alone without a conductor.[1]
In Japan, this is used in the operation of many trains and buses which are designated by a green sign on the front of the train reading (wanman (ワンマン運転 wanman unten)). The term wanman is the katakana transcription of one man.