New trains for Bedford (1): Midland Main Line bi-modes

This is the first in a series of articles looking at the new types of rolling stock that will come to serve Bedford within the next five years or so. Starting with the introduction of the class 700s on Thameslink a few years ago, the fleet serving Bedford will have been completely replaced by the early-to-mid 2020s, after several decades of stability, or at most incremental change (the High Speed Trains that currently provide some of the MML expresses, and the class 319s that worked Thameslink until recently, both started working into Bedford in the 1980s).

We’ll start with the new bi-mode trains that will be used for long-distance services between London and the East Midlands, and on to Sheffield. Of course, as is clear from a look at the service pattern specified in the invitation to tender for the new East Midlands Railway franchise, these won’t call at Bedford all that much. Nonetheless, they will provide three trains on weekdays after their introduction in (supposedly) 2021, nine on Saturdays, and more or less hourly services in each direction on Sundays.

Bi-mode logic
Before we get into what these trains might be, let’s think about what it means to run bi-mode trains, and what that implies. Though a caveat even before we get there: there remains a window, between now and the ordering of the trains, for the electrification of the Midland Main Line north of Kettering to be reinstated. As I observed previously, Secretaries of State come and go: from May 2010 to January 2018, the average tenure of a Secretary of State was around 27 months, and the railways have already enjoyed the dubious pleasure of Chris Grayling’s stewardship since July 2016 – 32 months ago.

It’s entirely possible that an incoming Conservative successor might follow Michael Gove’s pattern at the Ministry of Justice, and score some immediate policy and public relations wins by reversing Mr Grayling’s most obviously stupid decisions – among which the cancellation of the MML electrification scheme and others can surely be counted. It’s equally possible than any incoming Labour Transport Secretary would likewise reverse Mr Grayling’s decision. Of course, once the bi-modes are on order and under construction, it might be too late to change course – although depending on the timing, and the design selected, making a late switch and not adding any diesel power units to the trains could be feasible without much extra expense.

So, with that caveat: what are the merits of bi-mode trains? Even taking into account the saving on capital investment from not electrifying the line from Kettering northwards, there are very few. The franchise specifies that under diesel power, the new trains must be able to reduce the journey time from London to Sheffield by 20 minutes, and match the performance of the current class 222 ‘Meridian’ units, which have a top speed of 125mph and excellent acceleration for a diesel train of 0.79 m/s2 (metres per second squared, or metres ‘per metre per metre’). No design of bi-mode train has yet been developed that can meet this requirement. It may even be that the saving in journey time can actually only be achieved by missing out stops south of Leicester, including Bedford, as we know is planned, and the performance of any new bi-mode trains won’t assist with achieving that aim at all.

Why is this such a technical challenge? Philip Haigh gave a good summary in Rail 855, last year. A 5-car 222 has one Cummins QSK19 diesel engine under each coach, giving 3,750 horsepower (750hp per engine). The newest design of bi-modes in the UK are Hitachi’s class 800 and 802 trains: a 5-car 802 bi-mode has only three engines in total (MAN units), giving 940hp each, so only 2,820hp in total. Electrical equipment takes up space under the other coaches, plus the trains have the penalty of having to lug around the dead weight of their diesel generators when running on electric power – although at about 20 tonnes, this is less than five per cent of their total weight. However, the difference between the bi-mode and the ‘pure’ diesel train gets less as the trains get longer, as there are more carriages to put the diesel generators under.

The current bi-mode trains were designed on the assumption that the lines where the highest performance would be needed would be electrified, and therefore the trains would be using electric power; so the higher performance of a true express diesel train would not be needed. The scaling back of the Great Western Main Line electrification has voided this assumption, and in diesel mode the trains struggle to match the performance of the High Speed Trains they replaced (though if they were operating on electric power as often as originally envisaged, they’d be beating it comfortably). Clearly any trains with this level of performance could not meet the requirements of the East Midlands franchise.

Passenger experience is another consideration that shouldn’t be (but regularly is) overlooked: bi-mode trains have diesel engines underneath some of their carriages, which means that the noise and vibrations from the engines impinge on the passenger’s experience. In an electric train, this noise and vibration is absent, while in HSTs and traditional locomotive-hauled diesel trains, the noise and vibration is at least isolated at the end of the train, not directly underneath the passenger accommodation. If the bi-modes are introduced, it’s easy to imagine regular travellers becoming familiar with which carriages have engines underneath them and which don’t, and choosing where to board the train accordingly.

A final obvious drawback is the environmental impacts of the trains: whereas an electric train is fuel agnostic, and can be operated by electricity generated by renewable means or fossil fuel, bi-modes will inevitably generate both CO2 and particulate emissions when running on diesel power.

Bi-modes are not entirely without their advantages: they are far more flexible in terms of where they can travel on the network, and so can readily be run on diversionary routes when needed, or into platforms lacking electric wires. Then again, a move towards longer bi-modes could reduce operational flexibility, as they might be operated as, for instance, single ten-coach trains, rather than two five-coach trains that can take a single path up the main line and then divide to serve to different destinations – a common feature of current practice on the Midland Main Line using the class 222 Meridians.

So, now we’ve been through the issues around bi-modes, let’s look at the contenders to provide new trains for the Midland Main Line. Essentially there are two, but we’ll cover a third possibility for the sake of completeness…


GWR Hitachi bi-mode. Adapted from a photo by Hugh Llwelyn under licence CC BY-SA 2.0 and available for re-use under the same.

The only bi-modes currently being manufactured that might seem obvious contenders for the Midland Main Line are Hitachi’s family of class 800 and 802 bi-modes. However, a substantial development of the design would be required to meet the performance requirements set out above. It’s not clear that Hitachi is a shoo-in for the order though, even assuming a new design can be created.

The trains have their roots in the Intercity Express Programme (IEP), which dates back to 2005 when the DfT started a process to procure trains to replace the Intercity 125s / HSTs that had been introduced on the Great Western Main Line and East Coast Main Line in the second half of the 1970s. The programme’s scope also included the replacement of the Intercity 225s (Class 91 locomotives and Mark 4 coaches) introduced on the ECML after it was electrified in the second half of the 1980s. In development, the new trains were often called simply ‘IETs’ and the name is sometimes applied to them even now (as well as, less correctly, ‘IEPs’).

It was a controversial programme, held up by critics as an example of why non-expert civil servants should not be trusted with the detail of railway operations. Critics allege, probably correctly, that the end product is sub-optimal, and delivered at much greater cost (and delay) than it needed to be. The winning bidder for the programme was a consortium called Angel Trains, with the technology essentially supplied by Hitachi – hence the trains look externally very similar to the class 395 ‘Javelin’ trains used on the domestic services out of St Pancras along the Channel Tunnel Rail Link into Kent, aka HS1. Back in 2007, it was expected that the trains would be in service from 2015, but late delivery of both the electrification of the Great Western line and the trains themselves means they are still being introduced.

The ‘family’ comes in three variants:

  • Class 800 – bi-modes
  • Class 801 – pure electrics (OK, technically they have a small diesel motor, so they can move out of the way if they break down)
  • Class 802 – bi-modes with bigger fuel tanks. Originally, the 802 differed by having higher power from their diesel engines than the 800s, though output from the class 800s has since been uprated to match.

Although early reports that these trains couldn’t reach 125mph on diesel power seem to have been incorrect, they certainly take a while to get there – their weaker acceleration means they can’t match Meridian performance as required by the ITT.

The trains all have the same bodyshell as far as I can tell, and are therefore out of gauge for the Midland Main Line: the length of their coaches means that when taking curves their centres ‘throw’ to the inside to an extent that would mean they would strike platform edges. Hitachi will have to look at the carriage length to tender for the MML contract.


Promotional graphic for Bombardier’s bi-mode Aventras.

Derby’s Bombardier plant is currently turning out trains from its ‘Aventra’ family for London Overground, Crossrail Elizabeth Line and others. The London trains are massively late into service, as this is a new generation of trains whose every function is built around software (not unlike the class 700s, which endured a similarly tortured introduction).

Current tribulations notwithstanding, Bombardier has confirmed that it is developing a 125mph bi-mode Aventra, no doubt with an eye on the MML tender. Though that was about a year ago, and the project’s webpage on the Bombardier website has since been taken down, with no word of any developments regarding the trains since the initial press reports.


Promotional image by Stadler of their FLIRT trains (I think strictly speaking this is an electric version, but the bi-modes have essentially the same look).

One further manufacturer is producing bi-modes for the UK, but in truth Stadler seems unlikely to be in the running to supply the MML trains. Its FLIRT family is aimed at cross-country services that don’t require sustained 125mph running. Interestingly, they get round the problems associated with under-floor diesel generators by having a short, dedicated coach in the middle of each train that contains the diesel generator – effectively like putting a diesel locomotive in the middle of an electric multiple train. It’s quite an interesting solution, which passengers on Abellio Greater Anglia and the new Welsh franchise will get to experience. Fortunately the trains look good in a white livery with red highlights.

At present, the introduction of new train fleets on Britain’s railways is a total disaster area. Many fleets are being replaced by exciting new trains, and every single one of those processes is running catastrophically late. Partly this is because modern, software-oriented rolling stock is so complex that it’s difficult to get it running reliably in the demanding environment of a busy railway network. But partly it’s because of other factors, including optimism bias and complications arising from infrastructure work not being completed on time. So, whatever trains are selected for the Midland Main Line’s next intercity express fleet, you can safely bet your house that they won’t be running on the timescale required by the ITT.

Biobliography / further reading
Bi-mode trains: Unlocking opportunity? – Rail Engineer, October 2017
Bi-modes and Western Wire – Railway Magazine, March 2018
IEPTrain website.

Cover image adapted from a promotional rendering by Bombardier.

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