If the Underground was built today how would it be different

[roythebus]

The Adkins-Dawson system mentioned on page 1. A bit like the San Francisco cable car system then? A constantly moving cable with a grip to make the car go and stop.

I'd suggest if the Underground were to be built today, it may well be to the larger European loading gauge to enable the use of double deck trains.

As for gauge limiting the size of trains, have a look at some of the US railroads that run triple stack container trains on standard gauge. Maybe Stepghenson got it right. All containers ar 8' wide as it's the biggest "usually" allowed on road vehicles and has become the world-wide standard. Much like 25kvAC seems to be the new world-wide standard for electrification.

[brigham]

I've never heard of the Adkins-Dawson system.
The Adkins-Lewis system is a helical shaft drive mounted centrally between the running rails.
There is no 'grip'. The shaft turns continuously, and the speed of the cars is governed by the pitch of the helix. There are no 'stops'.

[class411]

Perugia uses the Adkins-Dawson system and when you look at the workings you wonder how it can operate reliably, dragging a several kilometre long cable round and round on pullies.

[ijmad]

Bit of a future-gaze, but personally I'm quite interested in whether there's a place for Personal Rapid Transit in the metro space. I'm imagining a very small train 'capsule' with 4-8 tip-up seats which are fully autonomous (routed by a central computer), and can provide a one seat ride between any pair of stations systemwide.

During rush hour, passengers can be grouped together using intelligent software, e.g. tell the system where you're going as you enter the station and it'll group you with a couple of others who want the same route. And perhaps the cars can run in groups.

I realise you'd lose space efficiency from the smaller sized 'trains' but you'd gain a lot of flexibility being able to run the 'cars' very tightly together and you'd have no interchange passengers at stations which would save capacity there too.

[philthetube]

Bearing in mind that the Victoria line alone shifts approx 1000 people every 2 minutes I really can't see this working.

[ijmad]

Feb 27, 2021 15:52:29 GMT philthetube said:

Bearing in mind that the Victoria line alone shifts approx 1000 people every 2 minutes I really can't see this working.

Hah, for sure, it's not gonna work on a line like that! 

[rincew1nd]

Feb 26, 2021 21:38:14 GMT ijmad said:

Bit of a future-gaze, but personally I'm quite interested in whether there's a place for Personal Rapid Transit in the metro space. I'm imagining a very small train 'capsule' with 4-8 tip-up seats which are fully autonomous (routed by a central computer), and can provide a one seat ride between any pair of stations systemwide.

During rush hour, passengers can be grouped together using intelligent software, e.g. tell the system where you're going as you enter the station and it'll group you with a couple of others who want the same route. And perhaps the cars can run in groups.

I realise you'd lose space efficiency from the smaller sized 'trains' but you'd gain a lot of flexibility being able to run the 'cars' very tightly together and you'd have no interchange passengers at stations which would save capacity there too.

I'm sure I've seen evidence somewhere that this kind of system simply can't shift the volume of people involved compared to a conventional metro system.

[zbang]

(back of the envelope calculations when I should be out in the garden)

I think it's a fairly simple calculation of floor-space and time. For a given available width, you can sit X people across; call it 10' and 6 people. A small carriage will need seating plus front/rear buffer space (4' each?). So a 12-person carriage will need two rows (5' each?) plus maybe 8' buffer equals 18' for 12 people. Hardly efficient, space-wise.

If you could make those work, there's still the issue of headways and switching. Coupled up into trains, this could approach current TPH headways (although probably not capacity), but individually you'd still have to time-separate the carriages at least somewhat (5-10 seconds?), which further reduces the track capacity. Add "dead time" around facing points movements and that further reduces throughput. Oh, and accel/decel times as needed.

I'm sure there are other factors I've missed.

[brigham]

I decided to study Personal Rapid Transport about ten years ago.
My conclusion was that it is a high-cost, low-volume system suitable for keeping motor cars out of city centres, as an alternative to public transport.
The city I used for the study was Sunderland, a seaport on the Durham coast.

[quex]

I think it's notable that in 200 years of "gadgetbahn" "innovation", nothing has yet to properly supplant the basic traditional railway in the roles in fulfils and has fulfilled for the past 200 years.

On the flip side, the canals were a dominant transport technology for about 100 years. Railways came along, were better, and so more-or-less replaced them. The fact railways haven't gone the way of canals tells me that they're still just about as good as doing their job (if not better) as they always have been. Thus there's very little need for concepts like PRT, maglevs etc. in many, if not most circumstances. They have their place, but that place is almost always a very very small niche.

[spsmiler]

Many people see maglevs as offering a futuristic type of urban railway which needs significantly less line inspection and therefore is cheaper to operate. This is in comparison with steel wheel railways which need constant checks on the state of the tracks, the rail fixings, etc. Real-world experience with maglevs however is not quite as rose-tinted as one might think.

Apparently the Japanese Linimo urban maglev cannot carry crush loads of passengers - because there will not be enough lift for it to rise up and float over the ground. Hmm, I've never heard of the London Underground leaving passengers behind because the train is too heavy and therefore cannot travel!

(crush loads and simply 'full up' is a different issue)

[Dstock7080]

Mar 1, 2021 19:29:22 GMT spsmiler said:

Hmm, I've never heard of the London Underground leaving passengers behind because the train is too heavy and therefore cannot travel!

There were many occasions during the early introduction of D Stock that trains were “tipped out”, “detrained” at Bow Road westbound due to the doors failing to close or even budge when fully loaded.
It was thought that the cars left Birmingham in with a slight upward curve to the under-frame and with a heavy complement of passengers this straightened out the under-frame but then buckled the door apertures.
After adjusting the door runners, the problem gradually disappeared as the cars aged.

[brigham]

The only MAGLEV system I have ever met was later replaced by cable!

[spsmiler]

Mar 1, 2021 20:30:00 GMT Dstock7080 said:

Mar 1, 2021 19:29:22 GMT spsmiler said:

Hmm, I've never heard of the London Underground leaving passengers behind because the train is too heavy and therefore cannot travel!

There were many occasions during the early introduction of D Stock that trains were “tipped out”, “detrained” at Bow Road westbound due to the doors failing to close or even budge when fully loaded.
It was thought that the cars left Birmingham in with a slight upward curve to the under-frame and with a heavy complement of passengers this straightened out the under-frame but then buckled the door apertures.
After adjusting the door runners, the problem gradually disappeared as the cars aged.

Oh my goodness - I've heard of clothes shop sales staff suggesting that something they are trying to sell which is brand-new and also very slightly ill-fitting will 'fit perfectly with wear' but never expected this to apply to trains too !!