eli5 Why do trains sometimes have one engine facing forward and an engine attached facing the back in succession?

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A train just passed by my house and I noticed this and now I’d like to know why companies do this I’m assuming its just easier but I’m hoping it’s something more interesting

In: Engineering

3 Answers

Anonymous 0 Comments

I can think of several reasons,

– train engines are pretty expensive. Their maintenance schedules are based on operational hours. And for obvious reasons, you may violate your warranty contract if you deliberately exceed the maintenance schedule constantly. When an engine is running, it adds up operational hours. When it’s just coupled on for no obvious reason, it’s just a very heavy wagon that tags along.

– The signal system on railroads – no matter with signal system that is in use – creates safety by moving trains apart so far that they cannot hit each other. Running one train with passenger cars and one train where you just move an engine elsewhere, will for obvious reasons take up nearly as much track time as running two passenger trains.

– privately owned railroads charge operators for the amount of time that they claim the railroad. If you have an engine that needs to go alone on a track, it’ll be nearly as expensive as having it pull passenger cars in the first place. But with nearly no income.

– maybe you plan on loosing the extra engine someplace along the passenger route, and have it fetch 25 newly loaded wagons from a steel mill? In that case, that driver probably appreciates that he can be on the passenger train. Sleeping. Because he is going to be driving that steel through the night.

– maybe the last engine is just in the wrong place and needs to be moved somewhere else? If there is a container ship expected on Tuesday-ish, you probably don’t want 20 extra engines in the harbor on Friday. In fact, you probably want them busy hauling cargo TO the harbor so that there is a lot of goods to pick up on Monday at the latest, and then you want to haul goods from the harbor Wednesday and Thursday.

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