Victoria n/b

Yes there were plans for two northbound platforms at victoria. This was the original idea until cutbacks effected the construction of the line. Thats one of the reasons of the dull grey tiling as the original pre war plans were stuck to instead of bringing some of the things up to date

It was also mooted in the original plans that the tunnels would have been mainline guage as well as having a couple of extra stations.

Trouble is, an island platform is more dangerous when overcrowded.

Ah, but then you run into the risk of passengers customers falling off the alighting platform and landing on the positive rail...

Oh yes, sorry. Didn't read your post properly.

I should say that the current operational constraint on the Vic is not extended dwell times at Victoria N/B but actually reversing capacity at Brixton.

Yeah, well the business case for using the middle platform to 'run through' would be poor on its own.

As you say, reversing capacity is an issue (actually the main issue) and running via a loop was the best solution compared to an additional platform at Brixton.

Thanks for mentioning that. If it was ever implemented, I would quite like to be invited to the official opening

I don't know of any existing metro termini of that design. However NYC has a few termini and reversing points where flying junctions are used for trains reversing in sidings. This is mainly due the 4 track layouts found on the NYC subway. There was (in the 70s) a plan for a partially grade seperated 4 platform terminus on the 2nd Av subway. A partially grade seperated underground 8 platform terminus is soon to be under construction for the LIRR East Side Access at Grand Central.



I would expect that after the signalling is upgraded on the Victoria Line, that the layout for the reversing loop could be re-designed with tighter curve radii. (The original loop plans, I would expect would have to have been designed for a 400m curve radius suitable for 50mph running as with the rest of Victoria Line). The tighter the curves, then the shorter the tunnelling, and thus the lower the construction costs. But not so tight that that speeds are lowered enough to restrict line capacity or increase maintenance.

Anyway, before building expensive projects, maybe ways of increasing capacity using the existing infrastructure should be looked at e.g closing doors shortly before the green signal is given at Brixton could save over 10secs. The new signalling and trains should increase reversing capacity at Brixton slightly as well.

No, more like tha aforementioned problem of people holding doors open!!

How practical would that be (I don't know the layout of Brixton station, sorry) - they do a similar thing at the Cross with GNER services.

One of the reasons why a well designed and operated reverse in platform terminus has a lower capacity than a well designed and operated reverse in siding terminus, is simply the additional time that it takes for the doors to close after the green signal is given.

I've given my opinions on the various things that could be done to allow for more prompt departures from Brixton (post VLU):-

1) PEDs - These tend to reduce the number of people obstructing the doors, as well as other well known benefits. But "first attempt" door closing is longer than if they wern't used. They also cost quite a bit to install, and increase the chance of technical problems that can delay the service. They could be useful in conjunction with number (2).

2) Early door closing - This could be initiated by using a countdown clock, as on the 92TS. When the timer gets to say 20 seconds till departure time, an alarm is given to tell the driver to do the announcements and initiate door closure. This would be more complicated for conflicting crossover movements (e.g a train due to depart from the ex-inbound platform), the system would have to be able to estimate how long it will be until the crossover is clear, and a green signal can be given. I don't know of any ATO systems which can do this, but it's not exactly beyond the realms of technology. Another potential problem is that you don't want the train sitting idle in the platforms with the doors closed, so the system would have to be able to predict the time to departure accurately for these conflicting movements. use of PEDS would prevent passengers interfering with a train that is idle with doors closed waiting for the green signal.

3) Automatic gates preventing access to platforms immediately prior to departure - This has been done in the past in Paris, and for different reasons at Oxford Circus. There is little doubt that it could be effective. But fire safety reasons, and passenger flow reasons would probably prevent its use as Brixton has a reasonably small circulating area.

4) DMIs/next train indicators directing passengers to other platform immediately prior to departure - This could be used in conjunction with (2). At a set amount of time before departure the DMIs could change to direct passengers to the other platform (assuming that is where the following train will depart from). At present the DMIs/next train indicators only change after the green signal has been given. This time before departure would have to be carefully selected, so as not to annoy passengers who have been directed onto the following train working out that they could have caught the first train. Also some members of the public arn't very good at following next train indicators anyway!

It's for those reasons that automatic gates at the platform access areas, near to the bottom of escalators would not be good idea!

I've read elsewhere that the portillon gates were removed when the line capacities were upgraded after the introduction of ATO, and trains with more passenger friendly doors were introduced (as opposed to the Sprague finger breaking doors).

The problem with next train indicators at Brixton is that the departing train receives a green very shortly after the inbound stops - sometimes only a few seconds which would mean that a DMI set to change early would point to an empty platform.

Automatic doors from the concourse could work well I think as there would always be an opening to one of the platforms. They would only need to close when the next inbound went over the crossover. Psychologically I don't it would upset too many people as they would be able to hear the next train entering the platform so would know that there was not a long wait. The morning peak at Brixton isn't really that busy so there would never be a danger of a queue. The barriers could be like the exit barriers on the Madrid Metro that are held shut with an electromagnet which is released if someone tries to exit and cuts a beam or if the power fails.

On another point StephenK could you explain how a reverse in siding terminus would be quicker? I'm not disputing it - I think I'm just being thick in failing to see the difference from using stepping back as they do at Brixton.

All this has been discussed in detail on another thread recently: colin will post the link when he reads this......



but basically the reverse in sidings is quicker due to

1.No conflicting passenger movements

2.Fewer conflicting train movements.

Unfortunately LULs tipping out rules mean that adding a reversing siding at Brixton, and thus having a single arrival platform would significantly reduce capacity. The better options would be a 2 platform passenger loop, or a flying junction terminus. A reverse in sidings terminus with 2 arrival platforms and 1 departure platform would be fine for the capacities needed, but would be expensive to build.

Do you mean something like at La Courneuve on Line 7 in Paris. Two island platforms, three tracks, two reversing sidings positioned one behind the other (as opposed to next to each other), and the possibility of trains to reverse in the centre platform track as well. This is probably one of the best designed termini on any metro, and not surprisingly turns 36tph, and could turn many more. Unfortunately it would be difficult and expensive to build a deep level equivalent.