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
Railway sorting yards, where railcars are assembled into trains are built with a small incline to start with, so a car needs only be pushed off and it will go through the switch maze using gravity. Of course there are speed measuring stations and braking equipment to make sure the cars don’t go too fast.
Because trains have brakes and this whole thing is unnecessary and complicated. The extra work needed for each station to accommodate this is not worth the minimal benefits.
[The original 1904 NYC subway was built this in this way.](https://secretsofthesubway.files.wordpress.com/2021/09/33_2-1.jpeg)
The platforms have since been lengthened to more than double their original length so the humps aren’t in the right places anymore.
Trains often use regenerative braking, similar to electric cars. But instead of saving that energy in a battery it is just fed back into the grid. This way they can slow down and return some of their kinetic energy to the grid.
Do the maths! E = 1/2 mv^2 = mgh
h = v^2/20. So even at 20m/s, you need to climb 20m to stop. for a 30m/s train, that becomes a 45m climb!
This is clearly impractical for anything except tunnel-bored train lines. And even then will add big expense. Maybe regenerative brakes would be easier?
On subways they sometimes actually do this.
The problem with doing it on some other types of railroad, is that not all stations are served by all trains using the track. If your train is supposed to just keep going past a station and not stop there, then it’s still going to be affected by the uphill into the station and the downhill away from it, and it wastes energy for the train operator to have to adjust for that each time.
This is done, for instance on the Victoria line on the London Underground. It’s only really practical in bored tunnels where it doesn’t need any extra earthworks. The other issue is that if you change the location of stations on the line this can work against you; it really reduced your flexibility. In the case of the Victoria line there is a very low likelihood of moving stations or adding them due to the expense of tunnelling and the fact the line has very regular spacing. Trains can only go up very shallow slopes, so even if this is happenning, it wouldn’t be perceptible at the station.
I imagine this could cause a headache for higher frequency lines. Sometimes a train “catches up” to the train in front and has to slow down and possibly wait at the signal before the station. This would mean they would have to go uphill when they are starting up again when the station is clear.
They sometimes are.
From [Wikipedia:](https://en.wikipedia.org/wiki/London_Underground_infrastructure)
>Many of the central London deep-tube line stations, such as those on the Central and Piccadilly lines, are higher than the running lines to help with deceleration when arriving and acceleration when departing.
There are limits to the slopes tracks can have though and those tend to be very light. Trains and trams etc aren’t good at going up even slight inclines compared to cars. So there is only so much this sloping can do.
If you do this in Satisfactory (the game), then over about a km you can get about a 5% benefit. Yep, I tested it. No, I don’t know why…
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