Definition of "crewless"

The short but extremely busy subway shuttle service on the northerly track between New York's Times Square and Grand Central Station will soon be provided by crewless three car trains.

1961 February, “Talking of Trains: Automated trains in New York”, in Trains Illustrated, page 78

A device for the automatic control of crewless helper locomotives cut into the make-up of heavy freight trains has been perfected by the Louisville & Nashville RR in conjunction with the General Railway Signalling Co.

1964 November, “Automatic helper locomotive control on the Louisville & Nashville RR, USA”, in Modern Railways, page 354

No hands on deck: Dawn of the crewless ship

2013 December 26, Dave Rudd, “No hands on deck: Dawn of the crewless ship”, in The Financial Times