deadhead vehicle; out-of-service vehicle
Refers to a train, bus, taxi, or other vehicle being moved without passengers or cargo, often for repositioning or maintenance. The English term 'deadhead' is common in transit contexts.
After the last train, the deadhead train returns to the depot.
When a taxi is running as a deadhead, you can't get a ride.
Compound of 回送 (かいそう, 'forwarding' or 'sending back') and 車 (しゃ, 'vehicle').