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Hands up – who told Alistair Darling about double deck trains?
My father is about 5 ft 8 inches tall. Born around three decades after him I am 2.5 inches taller. Move on another three decades and both my sons are a good three inches taller than me. Meanwhile, tunnels on commuter routes have remained much the same size
This is, of course, a statistically meaningless sample, but we know from military records and more recent government surveys that the population is getting bigger, both in height and girth. And this is particularly relevant to Transport Secretary Alistair Darling's call for an ‘imaginative' approach to evaluating ‘workable and affordable solutions' to increase capacity in the future.
Giving the keynote address at the Railway Forum's Annual Conference on 21 June, Mr Darling was clearly very unhappy with ATOC's future policy document, released the same day. This suggested that if growth continued it would become necessary to price-off peak hour traffic. ‘ Pricing people off trains full stop is not a transport policy at all', he snapped in reply to a question from the floor
That said, while pricing people off the railway ‘isn't the answer', ‘We do need more capacity', and one solution being evaluated by DfT Rail is double deck trains. Mr Darling had ridden in one in the Netherlands the previous week and told the conference ‘We need to see whether that solution could provide us with additional capacity in the medium to long term'.
And this is a serious initiative, part of a study being led by Director Rail Strategy & Finance Mark Lambirth into the costs and benefits of various capacity enhancement options. Mr Darling conceded that there would have to be structural changes because of gauging and related issues, adding that double deck stock is ‘just one example of how we need to look forward to fix the problems we know we are going to have in future'.
This raises an interesting question. Given that the drive over the next five years is to reduce the cost of the railways to the taxpayer drastically, why is DfT looking at a very expensive and limited solution to increasing capacity?
Ignoring the practical issues for a moment, double-deck trains are an all or nothing approach. Until you have gauge clearance along a route, they can't run. That means incurring all the associated infrastructure costs up front before you can start to earn a return.
Contrast this, for example, with longer trains where, with selective door opening, you need to lengthen platforms only at busy stations and terminals. And the cost of lifting bridges and opening out tunnels for double deck would more than pay for permanent capacity enhancements, such as eliminating of flat crossings.
All that said, and discounting the possibility that evaluating something unlikely is a good way for Government to defer doing something useful, a fresh look at double deck is justified. It is, after all, 55 years since the Bulleid Class 4DD prototype coaches entered revenue service on the London-Dartford route.
Bulleid was nothing if not ingenious and his solution was to have modular upper and lower compartments with facing bench seats, rather than two decks. The compartments were displaced longitudinally so that the footwell of an upper compartment coincided with the space between the seat backs of two adjacent lower compartment.
Each compartment had 11 seats and there was an extra low level compartment with 12 seats in the centre of the coach. There were also 12 tip-up seats on the top deck giving a total capacity of 156 seats. The single deck motor coaches could seat 120 and an eight car set could carry 1,104 passengers compared with 772 in a conventional eight car unit.
There were complaints at the time of hard seats and poor ventilation because of the fixed windows on the upper deck. For women travellers there was the fear of being trapped in an upper compartment with no way of escape. Even so the vehicles ran until 1971 before being withdrawn.
Operationally, the main problem was extended station dwell times since access to the upper compartments was through the lower compartments and up stairs.
Significantly it was hoped that DD units would avoid the cost of lengthening platforms (costed at £10million at the time) and buying extra units to run longer trains. In the event, longer trains won.
Back in the 21 st Century, the Vehicle/Structre-System Interface Committee (V/S-SIC) responsible for the new gauging policy considered the prospects for double deck coaches. Their starting point was a preliminary gauging analysis for a typical continental gauge double-deck train on the Paddington-Bristol main line.
Now you might think, as I did, that young Mr Brunel bequeathed a much more generous loading gauge than his north country rivals. But, according to informed sources who know about these things , the GWML has considerably more restrictions to UIC gauges than the West or East Coast main lines.
Electrification on the other two lines removed many restrictions, often replacing arches with flat spans. The GWML has kept many arches and now enjoys the tightest restriction among the UK 's Trans European Networks (TENs) routes.
Overall, ‘significant infrastructure work' would be needed to accommodate the sort of train the Secretary of State rode in. But the real show-stopper is the loading gauge at platform level and below.
Continental vehicles are obviously incompatible with the standard UK platform position. But even more significant is the stepped gauge profile below platform level which would mean either a reduced width on the lower deck, or even more expense on clearance.
And, as the Class 4DD showed, there are generic issues. Station dwell times, security, the increased risk of slips trips and falls on the additional stairs, not to mention managing upward and downward flows and emergency evacuation.
There is also the issue of the Rail Vehicle Accessibility Regulations where double deck trains would need a raft of exemptions. Would the disability lobby go along with the lack of step free access?
So, the V/S-SIC is clear that in the short to medium term, European double-deck stock could not run on the UK network. But, with one eye on Oliver, adds ‘It is possible that a radical approach to train design/layout could result in a feasible double-deck vehicle, but one has yet to be developed and proven.
This Policy does not therefore reject attempts to develop a UK specific double deck train but highlights the obstacles to its successful introduction.
Gauging policy document |
What about the prospects for UK gauge double deck, as opposed to modular compartments? Well, we are not alone. In Japan , the 1,067mm (3ft 6in) gauge commuter lines face similar capacity problems and have responded with double-deck electric multiple units, such as the JR-East Series 215 which entered service in 1992 and provides 1010 seats in a 10 car formation.
Worth noting is that the trains were intended to provide a guaranteed seat for long distance commuters – making loading and unloading less of an issue. The guaranteed seat also attracted a premium fare.
Maximum height above rail is 4,070 mm and this is the peak of a curved roof profile. Extending the similarity with the UK are platforms which require a vestibule floor height of around 1,200mm.
Double deck seating means dropping the lower floor between the bogies. With a 20m long vehicle, the lower saloon is around 10m long. Additional seating is provided in the vestibule ends.
Articulation increases the space between the bogies for a lower deck, but then you run into axle load, throw-over on curves and other issues which result in more, shorter, vehicles in a unit. Writing this I have started to appreciate that that the ‘Leader' notwithstanding, Oliver Bulleid was a clever old stick.
Compared with Japan , roof height of UK multiple units is typically 3,774mm and floor height 1,150mm. Assuming that the floor height in the lower deck was reduced to 200mm above the rails, the total height available for two floors would be just under 3.6m which. By the time you have allowed for the thickness of the upper floor and ceiling space would leave the headroom pretty cramped. This, I seem to recall, was the conclusion the Network southeast engineers came up with when they looked at double deck in the 1980s.
A more practical issue is fitting in all the systems needed by a modern train. Modern traction equipment is easier to package, but with the traditional underfloor location taken up by the dropped lower saloon and the roof space limited, designers would face real problems.
One option would be to have five car sets with three double deck trailers between two single deck driving power cars. But then the trailer coaches need their own auxiliaries such as air conditioning, air compressors for brakes and possibly doors. Retention tank toilets probable come under the ‘too difficult category.
So, double deck stock is still not the pancea for crowded commuter lines in the UK . And this analysis is what DfT's elusive new Director Technical & Professional would have told the Secretary of State on before he raised the issue of double deck stock in public. Oddly, no one has slipped me a job application form, but a chum at one of the ROSCOs is reported to be in the frame!