Train running to factory to re supply it. If the first car behind the engine is destroyed / separating the engine from the loaded cars. And the engine continues to the factory and arrives by itself. Is the factory resupplied? And if yes how much?
Trains (as well as truck or barge convoys) do not actually have to arrive at their target to resupply, as they do not actually bring something to their destination which then would reduce the downtime.
Actually their efforts are already as a given included in the object downtime timer. Only when you destroy a train car (the train engine is just another car for this purpose), a small amount of time is added to the time of already destroyed objects there (about 0.8 minutes, IIRC). So just stopping the train by smashing the engine (or one of the forward cars) has no impact on factory downtime at all. Only destroyed cars have.
raising a little snail 
And most significantly, playing other games
