Trivia: Most 'U shaped' platform in terms of gradient?

[modernrail]

When at City Thameslink I always notice how it is a u shape, with a gradient rising in either direction from the lowest point on the platform.

Are there any other stations with a prominent ‘u’ like this?

 

[AlbertBeale]

When at City Thameslink I always notice how it is a u shape, with a gradient rising in either direction from the lowest point on the platform.

Are there any other stations with a prominent ‘u’ like this?

The steep incline at the southern end of City Thameslink, before the end of the platforms, is needed to start raising the track level from being below the road at Ludgate Hill (this having been itself raised to give enough space underneath for the new rail tracks) to being above the road at Queen Victoria Street on the run-in to Blackfriars. The original line from Blackfriars to Holborn Viaduct went over Ludgate Hill (with some tracks on the west side, rather than going into the terminus, then diving down to access the Snow Hill Tunnel, which was rather higher at the point than the present City T/L tracks. At the north end of City Thameslink the rise up is to pick up the original Snow Hill tunnel vertical alignment.

Some Central Line stations on LU are the opposite - the majority of the platform is high up and it runs downhill at each end. (From the early days when this helped braking/acceleration when entering/leaving stations, and hence enabled a higher tunnel speed to be maintained closer to the station.

 

[LNW-GW Joint]

It's not in the same league, but the under-water Mersey Tunnel drops straight off the platform end at Hamilton Square in Birkenhead at 1 in 27 or 3.7%.
Merseyrail's drivers just ease trains over the lip and then let gravity do the rest until the climb out on the Liverpool side.
The drop on the Liverpool side is not as pronounced, with James St platforms some distance from the under-water section.

The Paris-Lyon LGV has a definite up-hill-and-down-dale feeling through the Burgundy hills with gradients up to 3.5% (1 in 28.6).
I think the Frankfurt-Cologne line in Germany has a similar profile in places
Such lines are unsuitable for freight however, and dual-purpose HSLs such as HS1 have shallow gradients.

 

[matchmaker]

Some of the stations on the Glasgow Subway have steep gradients entering and leaving - 1 in 25 for example at St Enoch.

 

[dosxuk]

Some Central Line stations on LU are the opposite - the majority of the platform is high up and it runs downhill at each end. (From the early days when this helped braking/acceleration when entering/leaving stations, and hence enabled a higher tunnel speed to be maintained closer to the station.

The same rules of physics which made it advantageous back when the Central Line was built still exist today, and is common across the entire Underground network, with even the Elizabeth Line making the same choice. It's less about the tunnel speed, and much more about using gravity to help you accelerate away from the station and then decelerate when arriving at the next one, saving energy when starting and reducing the amount of brake wear when stopping.

It also has the side benefit of meaning your running tunnels are deeper (where you're less likely to run into obstacles) but keeping your stations nearer the surface (which is easier to dig down to for the station entrances). Obviously, sometimes there are reasons you can't build it this way - I think there's a couple of stations on the Victoria line where the opposite is true as a consequence of their aim of building cross platform interchanges as much as possible and having to interact with the existing station infrastructure.

 

[modernrail]

The same rules of physics which made it advantageous back when the Central Line was built still exist today, and is common across the entire Underground network, with even the Elizabeth Line making the same choice. It's less about the tunnel speed, and much more about using gravity to help you accelerate away from the station and then decelerate when arriving at the next one, saving energy when starting and reducing the amount of brake wear when stopping.

It also has the side benefit of meaning your running tunnels are deeper (where you're less likely to run into obstacles) but keeping your stations nearer the surface (which is easier to dig down to for the station entrances). Obviously, sometimes there are reasons you can't build it this way - I think there's a couple of stations on the Victoria line where the opposite is true as a consequence of their aim of building cross platform interchanges as much as possible and having to interact with the existing station infrastructure.

Are these examples of an ‘n’ rather than a ’u’ though?

 

[AlbertBeale]

The same rules of physics which made it advantageous back when the Central Line was built still exist today, and is common across the entire Underground network, with even the Elizabeth Line making the same choice. It's less about the tunnel speed, and much more about using gravity to help you accelerate away from the station and then decelerate when arriving at the next one, saving energy when starting and reducing the amount of brake wear when stopping.

It also has the side benefit of meaning your running tunnels are deeper (where you're less likely to run into obstacles) but keeping your stations nearer the surface (which is easier to dig down to for the station entrances). Obviously, sometimes there are reasons you can't build it this way - I think there's a couple of stations on the Victoria line where the opposite is true as a consequence of their aim of building cross platform interchanges as much as possible and having to interact with the existing station infrastructure.

Indeed - physics is comfortingly consistent! But I think the obviousness of the slope at each end of the station is much clearer at some Central Line stations than I've seen it at the platforms of more recent lines.

 

[DynamicSpirit]

Indeed - physics is comfortingly consistent! But I think the obviousness of the slope at each end of the station is much clearer at some Central Line stations than I've seen it at the platforms of more recent lines.

Yep. And what that means is that there are likely to be very few other stations with the the u-shaped profile of City Thameslink, precisely because that's so disadvantageous to normal train running that you'd never build a station like that deliberately unless the local geography meant you had no reasonable alternative.

n-shape profiles on the other hand are very useful and therefore likely to be very common wherever a railway is built with stations in tunnels or on structures above ground so the slopes can easily be engineered with little additional building cost. (As I was writing that, it crossed my mind to wonder whether the DLR does that, since there are a lot of DLR stations on viaducts [*]).

[*] Is viaduct the correct word for the sections of DLR that are raised above ground level for long sections?

 

[DJ_K666]

The same rules of physics which made it advantageous back when the Central Line was built still exist today, and is common across the entire Underground network, with even the Elizabeth Line making the same choice. It's less about the tunnel speed, and much more about using gravity to help you accelerate away from the station and then decelerate when arriving at the next one, saving energy when starting and reducing the amount of brake wear when stopping.

It also has the side benefit of meaning your running tunnels are deeper (where you're less likely to run into obstacles) but keeping your stations nearer the surface (which is easier to dig down to for the station entrances). Obviously, sometimes there are reasons you can't build it this way - I think there's a couple of stations on the Victoria line where the opposite is true as a consequence of their aim of building cross platform interchanges as much as possible and having to interact with the existing station infrastructure.

On much of the Victoria Line (the one I've used most) you can actually feel the bottom of the incline and then the start of the gradient to the next station even before the train starts slowing down. It's very slight but if you know its there you know.

 

[d9009alycidon]

Some of the stations on the Glasgow Subway have steep gradients entering and leaving - 1 in 25 for example at St Enoch.

This was done by design, as it aided the original cable propulsion. A train approaching a station would detach from the cable and gravity helped slow the train into the platform.