crewless

adj

1. (not-comparable)Without a crew; unmanned

   “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.”

   “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.”

   “No hands on deck: Dawn of the crewless ship”