What future is there for the diesel train?

Stricter environmental laws, widespread electrification programmes and new developments in alternative forms of motive power are reducing the role of diesel traction on the railways. John W E Helm reports.

News that the much unloved Pacer units are to be replaced by ‘at least 120’ new diesel powered vehicles (for use in the North of England) has taken many by surprise. New build was not considered to be a realistic option in some quarters due to the expense involved, and only came about because the government overruled its own advisors on this point (as we report elsewhere in this issue).

However, the Pacer problem is part of the wider ‘diesel problem’ affecting the industry. The Pacers – and the Sprinters also, stem from the pre -privatisation era, and have to be replaced (in the case of the former) or refurbished (in the case of the latter), by or before, the decade is out. All passenger rolling stock – electric as well as diesel – has to be made PRM TSI (Persons of Reduced Mobility Technical Specification for Interoperability) compliant by 2020 -in order to meet tougher disability regulations – but new diesel trains bear an additional burden in having to meet ever stringent and expensive EU emission regulations.

Another problem is that the ongoing electrification programmes – on the Great Western and Midland Main Lines, as well as those in the North West and Trans Pennine areas – will reduce the demand for new diesel trains and displace many existing ones. The newer stock will be cascaded to other parts of the network, but the older units will be heading for the scrapheap, or heritage lines.

And future electrification projects will generate yet more uncertainty. Given the lifespan of a DMU is around 30 years, it’s hardly surprising that there is some reluctance in the industry to invest in new stock.

The future seems to be electric: That was the verdict of the all-industry Long Term Passenger Rolling Stock Strategy Steering Group (RSSSG). In February 2014 it reported on future national rolling stock requirements, forecasting a drastic reduction in the diesel fleet proportion from the current 31% to just 6% within the next 20 years.

Over 3,300 new passenger vehicles are currently on order for delivery between now and 2020, and most will be electric powered (apart from some bi-modal units and locomotive-hauled sleeping cars).  There have been no new DMU deliveries since 2011.

However, some lines will never be electrified (traffic levels would never warrant it), but they would still need to be operated by diesel trains (or by some other form of self powered traction).

The industry, therefore, appears to have three main options: (a) it can build new diesel stock; (b) refurbish and/or re-engine older trains; or (c) develop alternate forms of traction.

The first option appears the least likely due to cost grounds. The RSSSG report noted: “It is widely expected that present and future EU legislation regarding emissions from diesel engines (Directive 97/68/EC and its subsequent amendments, implemented in Great Britain as Non-Road Mobile Machinery (Emission of Gaseous and Particulate Pollutants) Regulations 1999 and 2013, known as NRMM) will increasingly make it difficult to procure and operate new DMUs having underfloor diesel engines, with an affordable business case. Indeed, EU consultation on further tightening of the rules is now underway.”

Existing legislation permits the continued operation of the existing DMU fleet. Spare parts and engine components are available, but the manufacture of existing diesel engine types is prohibited.

“The NRMM 2013 Directive contains an Extended Flexibility Scheme which allows engines on existing trains to be replaced with new Stage 111A compliant engines (rather than with the later standard Stage 111B compliant engines). The only Stage 111A compliant engine currently fitted to a British DMU is the MTU 1800 series engine fitted to the Class 172 DMUs built by Bombardier in 2010-11 (for London Overground, Chiltern Railways and London Midland). No TOC or ROSCO has to date needed to consider whether this or any other Stage 111A compliant engine might one day have to be fitted to any existing British DMU. Also, it is widely considered that it would be impossible to fit a Stage 111B compliant engine of adequate power to any of the existing British DMU types.”

Since 1997, EU directive 97/68 has been amended six times. RSSSG also fears that future tightening up could outlaw existing (ie pre Stage 111A) engines – almost the entire UK diesel fleet.

These EU regulations will be particularly harshly felt in the UK for two reasons: Firstly, on account of the higher proportion of diesel mileage in the UK than in many other parts of Europe. Secondly,   because of the fragmented way the rail industry operates. A DMU has a lifespan of around 30 years, whereas the length of rail passenger franchises is much shorter.  Sometimes – as in the case of the TransPennine Class 170s – the length of the franchise and that of the lease are not necessarily coterminous. On top of this, there is now the added uncertainty caused by delays in the electrification programme and the knock effect this will inevitably have on the cascade process.

The Pacer problem

The Pacer is the train everyone loves to hate; it is deeply unpopular with passengers, has few defenders, and is now on the way out. The trains were developed in the 1980s as low cost, bus-derived replacements for first generation DMUs. Today they form the backbone of regional services in the North of England: Angel Trains owns 188 Class 142 units, and leases 158 to Northern Rail; Northern operates all 56 of Porterbrooks’s Class 144s. Porterbrook also owns most of the 32 Class 143s, which are leased out to other TOCs.

“We don’t have enough vehicles to cope with existing traffic, and growth over the next 30/40 years will be substantial. Pacers are actually capping the number of passengers who travel. People simply can’t get on trains at times, and that is harming the growth of our cities,” is a common enough criticism, and one expounded to LTT by Rail North’s David Brown.

“With new trains, there will be a massive increase in revenue.  In West Yorkshire, for example, the introduction of new electric trains resulted in phenomenal traffic growth. Affordability (of new trains) is based on how the industry finances rolling stock; it won’t be four or five years, but more like 30 years, over the life of the asset. That should make it pay for itself. If there was enough demand for new rolling stock, I’m sure rolling stock manufacturers would make the effort, and that would drive prices down.”

However, an added complication is that any delay to the ongoing North West and Trans Pennine electrification projects will disrupt the cascade programme, so Pacers might have to struggle on beyond their 2020 sell-by date until new trains become available. LTT approached the DfT for clarification about the cascade programme, only to be informed that there isn’t one (despite rumours to the contrary in other parts of the rail press).

A Pacer: the train everyone loves to hate. A Class 144 on the Penistone branch.
A Pacer: the train everyone loves to hate. A Class 144 on the Penistone branch.

Brown is also Chief Executive and Director General for Merseytravel, and the authority is currently looking at a different business model for acquiring rolling stock. Merseytravel is also a franchising body in its own right  – unlike most other TOCs which are franchised by the DfT – and is considering buying its own trains to replace the ageing Class 507 and 508 electric multiple units (dating from the late 1970s) leased from Angel.

“As a public body we can borrow money at a cheaper rate than from the rolling stock leasing companies and give a long term certainty to the market.  That makes direct funding a very attractive option. We are finalising the affordability work, and will go back to our combined authority in the next few months for their decision on whether or not to proceed.”

The DfT decision to build ‘at least 120’ new diesel powered vehicles as replacements is estimated to add an additional £250m to the cost over the franchise life. ‘New’ means ‘brand new’, and that is not good news for two companies hoping to breathe new life into life -expired rolling stock (as low cost Pacer replacements).

Porterbrook has already spent £800,000 on refurbishing a Class 144 unit to meet the new PRM ‘regulations. A company spokesperson informed LTT that a production version would cost around £175K per vehicle, or £350K per two car set, as against around £3.5m to £4.5m for a new DMU set, and that it could operate economically for another 10 years.

Porterbrook says work with the Class 144 Evolution project (as it is known) has not been cancelled: “It is our opinion that a fully refurbished and modernised Class 144 train can and will offer a cost effective solution to the overcrowding partly created by rolling stock shortages. Even if the trains are not required long term by the new Northern franchise there may be an option for other routes and operators where a train that is economical to operate may be the difference between having a train service or not.”

Rival ROSCO, Angel Trains, had no plans to refurbish any of its Pacer fleet: Angel owns the (steel-bodied) Class 142s, whereas Porterbrook’s Class 144s are aluminium alloy-bodied and do not suffer from the same corrosion problems.

Vivarail’s plan to install diesel engines underneath redundant London Transport D78 electric District Line stock has also hit the buffers. Enough vehicles had been acquired (for an undisclosed sum) to form 75 two or three car diesel-electric train sets, and an experimental unit is currently undergoing tests. The trains were originally billed as Pacer replacements.

Sales director, Allan Dare told LTT that the engines, compressors, battery chargers, control systems brake resistors, and other parts would all be brand new. High power- to- weight ratio, rapid acceleration and low costs were the main selling points.

Vivarail is to acquire discarded electric trains from TfL and convert them to diesel traction.
Vivarail plans  to acquire discarded electric trains from TfL and convert them to diesel traction.

However, Vivarail is not downbeat at the DfT decision: “The accompanying Northern franchise ITT sets out a massive increase in train frequencies on lines that will remain diesel operated in the foreseeable future. It is probable that the requirement for additional DMUs will be somewhat greater than the 120 new-build vehicles specified by the DfT,” says Dare.  He is confident that Vivarail’s D-trains will be better able to provide, and less costly to run, than many of the ageing Class 150, 155 & 156 Sprinter units, not just in the north, but also in other parts of the country.

Both Porterbrook and Vivarail seem to be making the same point: the cake is growing and there’s food for every one i.e. for new build as well as for upgraded older stock. The DfT requirement is for 120 new vehicles, but Northern needs to replace 214 Pacers. Electrification will account for some, but the impact will be blunted by future traffic growth, and once the ‘Pacer problem’ is sorted out, the ‘Sprinter problem’ will have to be dealt with. All of which means there could well be a DMU shortage for years to come.

Alternative traction sources

Away from the heartlands of Pacer country, alternative traction forms are taking shape. What the industry requires is some form of self-propelled motive power that does not depend on expensive and extensive infrastructure works (like overhead electric wires or electrified third rails).

Battery traction is one of the strongest contenders: Battery locomotives and railcars have been around for nearly 100 years, though their application to date has been very limited.

However things could change if the current tests with the battery /IPEMU (independently powered multiple unit) prove successful.  The IPEMU is a joint industry project between Network Rail, Bombardier, Abellio Greater Anglia, Future Railway and the Rail Executive arm of the DfT. One car (of a four car) Class 379 Electrostar EMU has been converted to battery traction, and has just completed five weeks exhaustive testing (in normal passenger service) on the electrified Manningtree to Harwich Town branch.

It can take power from the overhead system or can operate on batteries alone.

“Only 60% of the rail network is likely to justify conventional electrification,” says Network Rail, “but 66% of non intercity DMUs (i.e. Pacers and most Sprinters) are over 20 years old.”

The IPEMU is regarded as an environment-friendly way of replacing ageing DMUs on short routes; ideal for extending electrification without the added infrastructure costs mentioned above; for short branch line work,  as well as bridging small gaps in the electrified network. The range is fairly limited (50 kilometres, or 31 miles), though that might be extended with future advances in technology. Several battery technologies have been tried; those on the train are of lithium iron magnesium.

So far Network Rail has remained tight-lipped about the project. It was unable, or unwilling, to answer specific points put by LTT, saying only that ‘the operating costs were comparable to that of a DMU’, but could provide no cost for converting to battery traction, though admitted that the extra weight penalty would add around five tonnes per vehicle.

Any future IPEMU is likely to be designed from scratch as a new unit, and would not be an adaption of an existing EMU type. More details are likely to emerge about the test results and the possible future role of battery trains when Network Rail releases its RUS electrification strategy document in March.

Battery traction is not the only option, however: electro-diesel (or bi-modal) locomotives have been running in the UK since the 1960s, and the concept will be used (by train builder Hitachi and diesel manufacturer MTU) to power some of the new IEPs  (Class 800)trains on the Great Western and East Coast Main lines from 2017/18 onwards. An electro-diesel is basically an electric locomotive, or EMU, fitted with a small diesel engine that can work over non electrified routes.

The electro-diesel brings greater flexibility but adds greater complexity.

UK train builder Bombardier floated the idea of converting some Class 22X ‘Voyager’ diesel-electric multiple units (DEMUs) to electro-diesel traction in 2010, and proposed installing additional electric vehicles in each set (to draw electric current from overhead wires). The project – known as Operation Thor – has not been abandoned. Bombardier informs LTT that the design feasibility has been completed but it would be up to the train operators/rolling stock companies to take any such conversion programme forward.

For shorter distances and lower speeds, another challenge to the conventional diesel comes from the Parry People Mover. Two four-wheeled (Class 139) PPMs have been successfully employed on the short Stourbridge Town to Stourbridge Junction branch line for several years now. The vehicles are ultra-lightweight and employ flywheel technology to store energy and provide traction, though a small motor is also used.

Two Parry People Movers already operate on the Stourbridge Town branch on the west Midlands
Two Parry People Movers already operate on the Stourbridge Town branch in the West Midlands

A larger bogie railcar is now under development, with the main components are housed within the bogie frame. Owner/inventor John Parry informs LTT that the class 139/2 could be a suitable substitute for a single car Class 153 Sprinter unit in some circumstances.

Unless or until  battery traction, electro-diesels and flywheel technology becomes more widely used and available, it looks as though the diesel train will be around for many years to come, albeit if only relegated to peripheral routes.

667/Mar 15









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