December – Ian Allan publishes his first book, ABC of Southern Locomotives, the first in a popular series which encourages the hobby of trainspotting in Britain.
December – First deliveries of USATC S118 Class "MacArthur" 2-8-2 locomotives, to Nigeria. There will eventually be nearly 800 built to the same basic design, seeing service on every continent, on or metre gauge.
December 6 – Schedules of fast trains around the United States are slightly lengthened to reduce wear and tear, following a wartime decision by the Office of Defense Transportation.
December 11 – USATC S160 Class2-8-0 #1604 (built by Alco) is officially handed over on loan to the British government at London Paddington station, from the first batch of 2120 for service in the European theater.
December 27 – Almonte, Ontario, Canada: Thirty-six people are killed and over 200 injured when a passenger train running late is struck from behind by a troop train.