Engines that can run in either directions.

I know that steam engines that can run in either directions. I thought that gas and diesel engines can't run in either directions until I found out that a passenger railcar built in 1910s had a gas engine that can run in either directions by moving the camshaft. From searching the Internet, I found out that some two-stroke engines can run in either directions but not 4-stroke engines. Marine two-stroke engines can run in either directions. The railcar must have a two-stroke engine. Search the Internet for McKeen Motor Car Company.

Diesels can run backwards by accident sometimes, setting fire to the intake air filter with the reversed hot exhaust gases. I'd guess this may be restricted to 2-stroke diesels like the Detroit.

I first encountered this "fun fact" in the Taiwan DMV ""Mechanical Knowledgee"" test which I took by accident, thinking I needed it for a Taiwan car drivers license.

Its apparently only required for truck drivers.

Would have been tough to pass since I have some mechanical knowledge and understanding, a severe handicap for any Taiwan test. About a third of Q+A were utter BS, but this is merely obscure.

The Messerschmit and Bond 3-wheelers had reversible engines instead of a reverse gear, giving them top gear in reverse, which must have been scary.

And then there is this system:

https://www.youtube.com/watch?v=_zR19_XDBgc