Driverless trains and the Underground’s deep tube programme

I have commented previously on the issues that surround the possibility of having ‘driverless’ trains on the Underground, and have seen no reason to depart from an earlier blog item and the subsequent article in Modern Railways (which can be found HERE). Of course, the suggestion that Underground trains might go ‘driverless’ any time soon was really a media misunderstanding of Mayor Johnson’s sabre rattling, but it served to get the debate going.

I have much sympathy with the idea that with technology leaping forward, drivers as we know them cannot sensibly be perpetuated for ever and a day, for the reasons I have set out earlier. What I had no sympathy for was the nonsensical suggestion that we switch over to a system such as the Docklands Light Railway uses, with its train captains in the passenger compartments. Heaven knows who put that forward, but it surely cannot have been a transport professional (so we can probably guess who).

It seems that since this hoo-hah first erupted London Underground has spent considerable time reflecting on how to proceed and the answer seems to leap out as a consequence of using no more than sheer logic.

The first thing to consider is that we cannot avoid looking forward for about 40-45 years because that is how long trains last (I wouldn’t care to comment about the signalling and control systems, but it will still be many years). The sub-surface lines and the Jubilee, Northern and Victoria Lines are either equipped with new trains and control systems or are in the process of being equipped, so for the time being they are out of the equation. That leaves the Bakerloo, Central and Piccadilly Lines (and arguably the Waterloo & City if it is to be dealt with as a separate entity). These lines are now part of what is called the ‘Deep Tube Programme’.

Of these, the priority for treatment is the Piccadilly Line. Although the trains are slightly more recent than those of the Bakerloo, the line is under far greater stress and some of the signalling and control systems are older, or at least more fragile. In addition parts of the line are shared with Metropolitan and District services and it would be desirable to have higher performance, automatic trains on the Piccadilly services that must share those tracks. Following a Piccadilly upgrade, the order would probably be Bakerloo then Central. What happens on the Bakerloo, of course, is dependent on the future of the Euston-Watford line and the mix of services there, and the fact Network Rail is the infrastructure owner.

The logic process works like this. With ‘DLR-style’ automatic trains ruled out as quite impractical on a line such as the Piccadilly, the choice is between a completely automated railway (that may or may not be ‘driverless’) and one that functions like the Jubilee and Victoria Lines where the train operates automatically but the train operator operates the doors. London Underground has concluded that full automation in deep tubes cannot be attempted without all kinds of safety systems in place some of which will take quite a bit of development. It would certainly need platform edge doors. By their nature, platform edge doors must have the door spacing at the same intervals as the doors on the train, so all the doors coincide. This presents a problem during any stock changeover in the event that the doors spacings of the old and new stocks are not the same (and bear in mind the Piccadilly Line already runs three slightly different formations).

London Underground has concluded that new trains cannot be the same as the old ones. For a start they want the new ones to be longer than the 1973 stock to take advantage of the full platform length to help improve capacity. There is then the thorny issue of the large gaps between doorways and platforms at certain stations to consider, increasingly frowned on by safety authorities. Without major reconstruction that might not even be possible at certain locations, or may be quite unaffordable, the best solution seems to be to introduce shorter carriages that even without using any new form of technology will significantly reduce the gaps. The thinking is to provide a walk-through train comprising shorter cars sharing bogies with the car adjacent: – maybe nine cars on eight bogies or something of the sort. There is another reason for doing this in that it makes the finished train somewhat lighter (bogies are very heavy) and this is going to be crucial if energy usage is to be reduced. In turn, energy reduction is vital in reducing heat generation in an already warm environment where service frequencies will rise appreciably, and it is hoped will also create a situation where air-conditioning may be possible. Air conditioning not only puts heat into the tunnel that then has to be removed, but because of losses it itself generates additional heat; the ideal would be for new trains with air conditioning to generate no more heat than the present trains do now, though additional means of getting heat out of the tunnels may still be necessary.

So, the new trains will be very different from the 1973 stock. That makes it impossible to install platform edge doors until the last of the old trains has gone. That means the new trains must have driving cabs, despite dark rumours being spread last year. It is of course true that cabs can be removed at some point in the future. What can be expected is that at least initially the new trains will be capable of running automatically with an operator controlling or supervising the doors. Whether the trains enter service in ATO mode or are driven manually is probably yet a decision to be made, but LU has enough experience either way. Only then, can platform edge doors be considered. I will not weary readers with the issue that those will raise, especially if anybody feels they are needed in the open air on tracks that are shared, but some challenging decisions will have to be made, and there are not yet answers to how such doors will function on highly curved platforms, though solutions can be conjectured.

With the best will in the world, from where we are now this looks like a 10-15 year programme during which time, no doubt, the other issues surrounding cabless and driverless trains in the deep tube will have been gone into. I would be surprised to see such a mode of operation in use on any of the deep tube this side of 2030.

Having said that, there are things that could be done. Automatic reversing in sidings or to and from depots, without staff on board, seems plausible. The Waterloo & City Line seems another possible candidate for experimentation, with just five trains. The issues are containable if things don’t work out as expected, and the platforms are relatively straight. Could this be ‘driverless’ any quicker?

I do wonder for how much longer London will tolerate running trains in tunnels not even 12ft in diameter though. 5 years? Obviously not. 250 years? Surely. So when between now and 250 years is something to be done? And what? Reasons for doing something include safety (no side escape as required on modern lines), viciously sharp curves in places constraining train performance and perhaps train size, amongst other reasons. Also, people are getting bigger. The BBC reported that between 1875 and 1975 British men at age 21 have grown in average height from 5ft 5ins to 5ft 10ins. One can have the debate about the precision of the statistics, but that both the height and weight of men and woman has gone up significantly is certain ground, and that heights are still increasing is also certain. If I have done my sums right the doorway of (say) a 1972 stock train is only 6ft 1ins and a significant number of people even boarding today have to stoop (including some women!). The maximum height inside, in the very centre, is only about 6ft 8ins and these trains have no ceiling clutter, which might not be the case with newer trains with air conditioning. I would suggest that it is at least plausible that in 100 years it will be unrealistic to expect to operate trains for much longer with half the occupants stooping, or nursing a banged brow obtained on entering the carriage through a low doorway.

Nobody really wants to bother about what their successors will have to contend with in a hundred years, and I only do so here because the time to start thinking about it is now. At least there should be a strategy, and maybe passive provision amongst other works that have to be carried out. We should not forget it has been done in the past on the Northern and Central Lines, though not on the scale that would be wanted today. If it is a horrendous prospect now, it will get more difficult, not less, as time goes on. Still, it is a more interesting problem to have than the one of running the system down as traffic drifted away, which is what was going on when I joined the organization. How times have changed!

About machorne

I have always lived in London and taken a great interest in its history and ongoing development. This extended into the history of its transport services, about which I have written a number of books - I have spent most of my working life working in the industry and observing changes from within, mostly to the good, but not always so. I continue to write, and have a website with half finished stuff in it so that it is at least available, if not complete. Several new books are in hand. I have many 'works in progress' and some of these can be found on my website; the we address is
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3 Responses to Driverless trains and the Underground’s deep tube programme

  1. Taz says:

    I hadn't seen the Modern Railways article before. It is an excellent summary of the current situation.


  2. Taz says:

    “The Piccadilly line will form the blueprint for a single train design that will be rolled out across the Central, Waterloo & City and Bakerloo lines over the next two decades.” (TfL Business Plan 2013, p.35) It is interesting that the Picc & Central are at the top of the list since they have the least tunnel running of the deep lines, under a third. If there were plans to reduce train staffing in open sections of line in the future these would show the greatest benefits, with the Bakerloo & Jubilee having about half in tunnels. The Picc & Central would therefore be the lowest cost lines to convert for sub-surface trains at their future upgrades. I wonder how disruptive conversion would be. Perhaps some of the more modern sections are straight enough, but the original tube tunnels have tight curves to be eased and curved platforms no longer acceptable. The most economic and convenient solution would probably be to construct new deeper tunnels with half the number of stations but double-ended to give as many top stations: new alignments also in some areas to meet modern demand, eg Central via Paddington. Higher running speeds giving added capacity could help to justify costs. What would become of the original tunnels? Could they provide weatherproof cycleways?


  3. Andy Brice says:

    I wonder if, instead of platform-edge doors (which have to be aligned with train doors) it would be feasible to use platform-edge barriers, which lower into the platform when trains arrive (thereby being usable with trains of any door spacing).

    As far as I'm aware, it would be new technology, but I can't think of any reason why it's an unworkable solution.


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