South Kensington station's escalator replacement project • Hacker News Board

Re: South Kensington station's escalator replacement project

#41

Post by Symbiote » Tue, Aug 17, 2021, 12:48 PM UTC

traceroute66 wrote: post #12

brainwad wrote: post #9

Earlier quoted context omitted.

Express services on shared track isn't common on metro systems. NYC's express subways all use dedicated track, for instance. The tendency to not keep to a strict timetable and the close-running of metro systems makes it hard to slot express trains into gaps between local trains properly.

> The tendency to not keep to a strict timetable and the close-running of metro systems makes it hard to slot express trains into gaps between local trains properly. To be fair, "close-running" is not a word that tends to be associated with the District line ... "signal failure" is, however ! ;-)

The central section (including the Circle Line) has a service interval of 2-2½ minutes, depending on the time of day.

The rest has roughly 2-10 minute intervals.

Re: South Kensington station's escalator replacement project

#42

Post by noneeeed » Tue, Aug 17, 2021, 12:55 PM UTC

adwww wrote: post #40

noneeeed wrote: post #15

Earlier quoted context omitted.

The only way to have express and stopping trains on the same track is to have frequent passing places. Scheduling and signalling get fiendishly complex. On somewhere like the underground, where building those extra passing places is really hard it just isn't worth it. This is one of the big missunderstandings about the HS2 line. Politicians focus on the shorter journey times, but the big win is actually increased cap…

Could you have odd / even trains that miss stops?

Yes, you can do things like that, but that ends up with you having two different sets of stations that are not easy to get between. The normal pattern is express trains that stop a few times with stoppers that "fill-in" between, but there will be different patterns of stopping to try and optimise for different groups of travelers.

Scheduling/timetabling is a wickedly hard problem, especially in a system like a railway, it's the sort of thing people get Maths and CS PhDs in. The contstraints that you have to solve are complex and interconnected and are part of a bigger network, and you are also trying to please a lot of people with very different (often contradictory) needs.

Re: South Kensington station's escalator replacement project

#43

Post by jfindley » Tue, Aug 17, 2021, 12:56 PM UTC

adwww wrote: post #40

noneeeed wrote: post #15

Earlier quoted context omitted.

The only way to have express and stopping trains on the same track is to have frequent passing places. Scheduling and signalling get fiendishly complex. On somewhere like the underground, where building those extra passing places is really hard it just isn't worth it. This is one of the big missunderstandings about the HS2 line. Politicians focus on the shorter journey times, but the big win is actually increased cap…

Could you have odd / even trains that miss stops?

This is already the case for some of the very low-volume stops on that line. For non-express trains a combination of the following is currently (or at least was pre-covid) in use, with the mix varying throughout the day:

  * stop more or less everywhere
  * stop only at larger stations
  * even/odd stopping at small stations

The scheduling already seems pretty clever, and that's just from observing as a passenger. I suspect behind the scenes there's a whole lot more to it that's not obvious to someone who is just trying to get to work.

Re: South Kensington station's escalator replacement project

#44

Post by traceroute66 » Tue, Aug 17, 2021, 12:56 PM UTC

adwww wrote: post #40

noneeeed wrote: post #15

Earlier quoted context omitted.

The only way to have express and stopping trains on the same track is to have frequent passing places. Scheduling and signalling get fiendishly complex. On somewhere like the underground, where building those extra passing places is really hard it just isn't worth it. This is one of the big missunderstandings about the HS2 line. Politicians focus on the shorter journey times, but the big win is actually increased cap…

Could you have odd / even trains that miss stops?

Yes, this was the sort of thing I was thinking for London. Not "express" per-se, but "missing stops" (i.e. just like what happens when stations are closed for platform maintenance during normal ops).

Re: South Kensington station's escalator replacement project

#45

Post by jon-wood » Tue, Aug 17, 2021, 12:56 PM UTC

adwww wrote: post #40

noneeeed wrote: post #15

Earlier quoted context omitted.

The only way to have express and stopping trains on the same track is to have frequent passing places. Scheduling and signalling get fiendishly complex. On somewhere like the underground, where building those extra passing places is really hard it just isn't worth it. This is one of the big missunderstandings about the HS2 line. Politicians focus on the shorter journey times, but the big win is actually increased cap…

Could you have odd / even trains that miss stops?

Not without passing places, because you can't miss a stop without the train in front of you also missing it, at least without an eye watering body count.

Re: South Kensington station's escalator replacement project

#46

Post by traceroute66 » Tue, Aug 17, 2021, 1:01 PM UTC

s15624 wrote: post #13

traceroute66 wrote: post #6

To be honest, for me the most interesting part of the blog post was this one-liner "for an unbuilt high-speed District line service between South Kensington and Mansion House with just one stop at Embankment.". As one of the millions who at some historical point in their lives has had to suffer the District line commute, the above is a thought I used to have regularly whilst stuck sniffing someone's armpit on the Dis…

The majority of the tube network is pretty much already at peak capacity, with trains on the Victoria, Jubilee and Northern being full autonomous with moving block systems as separation distance can now only be maintained through autonomous systems. I think an express service would be wonderful but it would require careful orchestration. I think it might be worth increasing the line speed through signaling upgrades a…

Isn't the problem with automation on the tube less the technology but more the unions ?

Re: South Kensington station's escalator replacement project

#47

Post by traceroute66 » Tue, Aug 17, 2021, 1:02 PM UTC

dspillett wrote: post #21

traceroute66 wrote: post #6

To be honest, for me the most interesting part of the blog post was this one-liner "for an unbuilt high-speed District line service between South Kensington and Mansion House with just one stop at Embankment.". As one of the millions who at some historical point in their lives has had to suffer the District line commute, the above is a thought I used to have regularly whilst stuck sniffing someone's armpit on the Dis…

For large parts of London's underground (and overground[†]) it is simply the case that it wasn't really designed — lines were slapped in willy-nilly by disparate commercial interests with relatively little forward planning, and only later became something like a coherent whole with some consideration for coordinated thinking. Once the lines are in, upgrading them is more difficult than building them in the first plac…

Thanks for the insight @dspillett, makes sense.

Re: South Kensington station's escalator replacement project

#48

Post by hogFeast » Tue, Aug 17, 2021, 1:11 PM UTC

Milner08 wrote: post #27

hogFeast wrote: post #26

Earlier quoted context omitted.

The govt bailed them out last year.

Right, cause covid. You know, when no one was using the service but they had to keep operating for front line workers... hard to make money when there are no users.

So they were profitable...discounting all the times they lost money.

Re: South Kensington station's escalator replacement project

#49

Post by noneeeed » Tue, Aug 17, 2021, 1:19 PM UTC

jfindley wrote: post #43

adwww wrote: post #40

Earlier quoted context omitted.

Could you have odd / even trains that miss stops?

This is already the case for some of the very low-volume stops on that line. For non-express trains a combination of the following is currently (or at least was pre-covid) in use, with the mix varying throughout the day: * stop more or less everywhere * stop only at larger stations * even/odd stopping at small stations The scheduling already seems pretty clever, and that's just from observing as a passenger. I suspec…

Yep, there are whole departments of people who work hard to make the scheduling on railways work as well as possible. People always like to complain, but they always ignore the fact that the timetable has to try and satisfy a huge number of people with often very different needs, on networks with some very fixed constraints that are expensive and difficult to change.

Re: South Kensington station's escalator replacement project

#50

Post by TheOtherHobbes » Tue, Aug 17, 2021, 1:19 PM UTC

noneeeed wrote: post #15

traceroute66 wrote: post #6

To be honest, for me the most interesting part of the blog post was this one-liner "for an unbuilt high-speed District line service between South Kensington and Mansion House with just one stop at Embankment.". As one of the millions who at some historical point in their lives has had to suffer the District line commute, the above is a thought I used to have regularly whilst stuck sniffing someone's armpit on the Dis…

The only way to have express and stopping trains on the same track is to have frequent passing places. Scheduling and signalling get fiendishly complex. On somewhere like the underground, where building those extra passing places is really hard it just isn't worth it. This is one of the big missunderstandings about the HS2 line. Politicians focus on the shorter journey times, but the big win is actually increased cap…

A high speed line with passing places is a non-starter.

The signalling barely works at the best of times. It's literally a museum of technologies, from the pneumatic to the electronic, and it's one of the most common points of failure on the network.

But when it's working it's been improved to the point where there's almost no spare line capacity at peak times.

And if you're making new tunnels it's so difficult and expensive to get a Tunnel Boring Machine into place that it makes no sense to bore short sections.

Crossrail is supposed to be London's east/west express line. Obviously it's not ideal for District Line users, but it should free up some peak hour capacity for Circle and Hammersmith & City journeys which may translate to fewer District/Circle passengers.

There's also talk of a north/south Crossrail 2.0, but that's unlikely to happen for decades.

There are overground express sections on the Piccadilly (District) and Metropolitan (Jubilee) lines but they all keep the lines separate.

There may well not be room for a tunnelled express in the central area. If it were up to me, I'd consider installing a good urban tram link from (say) Earls Court to Embankment.