Trains (whether its a subway/tube or a regular locomotive) travel very quick, and when approaching a station, they need to slow down to a stop.
Why not have the station be built slightly elevated from the tracks? so as the train approaches, it has to climb an upward slope (and therefore trade kinetic energy for potential energy)?
And then when it leaves the station, it can more quickly accelerate and gain up to its target speed? Wouldn’t this be more efficient?
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In: Engineering
This would potentially save you a little bit of fuel and brake wear over time, but it would also require moving thousands of tones of dirt to make the little hill. I’m sure that there are some train stations built like this, but it isn’t standard because it would increase the complexity and cost of building the train station without getting you much good in exchange. The cost/benefit breakdown just doesn’t favor it.
This is done sometimes, though more frequently on metro type systems. The Montréal metro is a good example. On mainline railway networks this is less practical, as not all trains stop everywhere, and it can result in some headaches from a design and maintenance perspective.
It’s not always worth it.
A lot of the time, any meaningful amount of height isn’t worth it considering how long that hill would need to be. Trains can only ascend very gentle grades, so raising the station by a few feet may mean you need to create a hill that’s a mile long. What do you do for all the level crossings and other infrastructure between the start and end of the hill? And what about trains that don’t stop at that station?
Most rail lines have service both ways. Going one way you wouldn’t have the hill to slow you down, going the reverse direction you would be going down hill and use extra braking.
The stations on the Victoria line of the London Underground were designed with a slight slope for exactly this reason.
In practice, it’s not common for new-build anymore because of level boarding requirements.
So while this could make sense for small passenger trains with few cars, in general slopes and hills cause issues with fright trains due to an increase in inter train forces. The slack between cars shifts as a train accelerates and brakes and you can easily get a knuckle break (the cars seperate) when slopes cause your train to have sections moving at different speeds. If your front end is accelerating down a hill while your back end is slowing down going up a hill, this strains the joints in trains.
A bunch of London Underground lines do this, they slope downhill as you leave the station and then rise again as you pull into the next one
This is indeed done – if you check out Plainly Difficult on youtube he recently did a video about a runaway train on the tube (or possibly metro) where he mentions this is a thing they do.
Berlin‘s subway has a lot of stations like this. The train leaves the station and is accelerated by a down slope and deccelerated by going up the ram of the next station.
Actually in many train stations you have such “hills”.. they will be used for managing wagons transfers.
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