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Further electrification of the UK rail network will not only be welcome but necessary for a full-scale phase-out of diesel-only trains, according to Rail Industry Association (RIA) technical director David Clarke.

“Electrification is better for the environment, quieter, costs less in the long term, improves journey times, is lighter and reduces delays,” he says. “These reduced journey times with new trains have been shown to lead to local economic growth in the areas served.”

According to the Institution of Mechanical Engineers (IMECHE), a mere 42% of the UK’s network is currently electrified, putting it behind the Netherlands (76%), Italy (71%) and Spain (61%).

Moreover, recent setbacks have created scepticism about future electrification projects. Massive budget overruns and delays caused the government to scrap plans to electrify railway lines in Wales, the Midlands and the North of England in 2017.

Escalating costs led to the Great Western Electrification Scheme’s budget rising from £874m in 2013 to £2.8bn in 2015. According to Clarke, this programme was included in the UK Government’s 2009 electrification strategy on the basis of a very early estimate of cost and scope, derived from the East Coast electrification scheme that finished in 1992. As a result, the overall price of the project was vastly underestimated.

“The rapid ramp-up and then repeated stalling and restarting of electrification projects has only helped increase uncertainty in the sector, also helping to increase costs,” says Clarke.

Progressing through to this year, the RIA’s Electrification Cost Challenge is an initiative bringing together a number of contractors, consultants and suppliers of electrification infrastructure to investigate what can be done to reduce costs.

Meanwhile, IMECHE head of engineering Jenifer Baxter says the Department for Transport (DFT) needs to instruct infrastructure owner Network Rail to develop an appropriate specification for railway electrification, which will enable it to build an affordable business case for a rolling programme of completion over the next 20 years.

“This is to complete the electrification of mainlines between Britain’s principal cities and ports, particularly the urban rail networks through major city centres,” she says. “That’s one area where we would say that there definitely needs to be a very particular focus.”

Johnson says the rail industry should look into new bi-mode technology and alternative fuels to power trains. But to what extent are these options a viable replacement?

Bi-mode trains are currently being introduced on the UK’s Great Western and East Coast routes. The major benefit is that the trains are able to switch between electrified and non-electrified tracks, enabling their use in areas where the installation of overhead catenary lines may be impossible.

Nevertheless, Baxter expresses that these trains could actually end up being more of a hindrance to rail networks. Bi-mode trains emit higher levels of CO2 in diesel mode than diesel-only trains, and their two-mode operation can lead to greater capital and maintenance costs.

“If you offer a solution to non-electrified lines that doesn’t provide the required performance or often the most efficient or environmentally friendly solution, I would suggest that it’s not the best possible alternative,” says Baxter.

IMECHE has recommended that the DFT conduct a series of trials to look into how new bi-mode trains operate in and out of major stations, as well as to understand the level of pollutants and their effect on commuters and railway workers.

Another potential solution is battery-powered trains, which would create zero emissions at the point of use, but the energy density of batteries is low compared with other fuels. Baxter says a lithium-ion battery offers 2.63 mega joules of energy per litre, while diesel provides 35.8, meaning that batteries would have to be huge to match the performance requirements of a diesel-only locomotive.

Future developments in regenerative braking could mean that battery-powered trains could create their own power in the future. “Battery-powered trains have the same ‘range anxiety’ as battery-powered cars, but there are many places where they could be used to avoid the need to fully electrify,” says Clarke.

One diesel alternative that has seemingly captivated the industry has been hydrogen. Trains powered by the substance only emit steam and store everything they need to create energy on-board. “You could use a fairly similar infrastructure for refuelling trains as diesel and equally you can refuel them very quickly, whereas a battery would obviously require charging,” says Baxter.

Rail technology manufacturer Alstom is in the process of introducing its hydrogen-powered Coradia iLintin Germany this year.

Alstom’s head of business development and marketing Mike Muldoon says a number of railways in the UK predominantly use diesel multiple units (DMUs) as they could never viably be electrified. With UK Government officials clamouring about the potential of the technology, there is a potential market for hydrogen.

“We have the second-largest fleet in Europe, and if you look at the age profile of almost the entire fleet of diesel-only powered trains, their life expires before 2040,” says Muldoon. “They’ve all got to be replaced, and that makes it potentially quite a large market.”

Last month, it was reported that the UK Rail Safety and Standards Board was working with Alstom to start a hydrogen pilot project by 2019 or 2020. While Muldoon could not confirm which lines will be involved in the pilot, he says the company is aiming at franchises operating regional diesel services with no plans to electrify.

With regards to both battery and hydrogen trains, Clarke says the government needs to provide further support to the industry in enhancing energy storage. Continued investment in research could lead to a modular plug-and-play approach, allowing rolling stock to be retrofitted with alternative sources of power.

“Once the technology is adequately demonstrated in the UK or internationally, the government should ensure that their output specifications and evaluation criteria in franchise competitions encourage the adoption of this new technology,” he says.

According to Clarke, the 2040 deadline is “rightfully ambitious” and sets the industry a challenge that it can meet. But he and Baxter both stress that political and financial support will be crucial for the sector.

In addition, the government needs to be careful not to make rail less attractive in the process. For example, rail freight companies have expressed concern that the deadline could damage the case for freight sector investment in favour of road freight.

“This would be counterintuitive and not environmentally beneficial, so these concerns must be allayed by the government,” says Clarke. “Careful consideration must be given to how we achieve the goal whilst providing some policy certainty to rail industry investors and avoiding damaging the viability of railway businesses.”

“It will require a clear strategy which reassures investors, encourages the development of new technology and maintains and enhances the environmental credentials and business competiveness of the rail industry.”

Johnson has given the rail sector until later this year to come up with a plan for how it will begin phasing out diesel-only trains. But with locomotives at various stages of their lifespans and alternative fuels still reliant on developing technologies, the industry still has a long way to go.