how do you know ? back in the 70s I worked briefly one summer on the night shift as fireman on a diesel loco that moved cars for Bethlehem Steel. So figuring I'd be up all night working I slept that afternoon, go to work at 11, we move cars around for maybe 4 hours, park the loco and the brakeman and conductor call it a night, the engineer says you're the new guy so you have to stay in case we have to move more cars, but for now get some shut eye - luckily I had brought a book. Going forward I was always happy to jump out and "line the irons" if only to stretch my legs instead of just sitting on my *ss. Then one night the train crew has me throwing switches, I ask where we are going and they say "you'll see" and we take the loco to a remote part of the plant behind a large empty building, I see flames, lo and behold these guys are having a bbq at 2am, quaffing beers and partying it up along with a few ladies of the night in the mix. No small wonder the freakin steel industry got walloped by foreign competition as these were highly paid workers that rarely put in 8 hrs.That "hybrid engine" in a freight train is a V-16 supercharged diesel engine, coupled to a generator to produce the power to the drive trucks to move it. There is NO battery reserve, shut off the diesel engine, no power!
Ask me how I know.
But like the fireman's job eventually was eliminated the long term future of the gasoline engine as the prevailing power source is in doubt.