Almost a year ago, in the May 2017 issue, we wrote about the implications for rail freight of measures to improve air quality. Since that time, the agenda has moved on, with Government committed to restricting the sale of diesel cars and vans from 2040, and more recently the challenge from Rail Minister Jo Johnson to decarbonise and eliminate diesel-only trains by the same date (p11, last month).

As we outlined back then, the rail freight industry trades on its superior environmental performance, particularly in respect of carbon, with 76% less CO2 per tonne moved than the equivalent on road. Rail also has advantages in NOx and particulate emissions. Yet the pace of change in road technology means we cannot be complacent about this advantage and must continually look to improve. It is easy to think that resolving air quality concerns and decarbonisation are the same issue, but in reality the policy timescales mean they must be considered as interconnected but distinct policies. We need to look at the short-term interventions which are possible now, having regard to the long-term requirement to replace diesel fuel.

In particular, the case for investment in rail freight today must be protected, and any sense that the locomotive fleet will become a stranded asset is deeply unhelpful in that regard. The current diesel fleet stands at between 500 and 600 locomotives, the vast majority of which are less than 20 years old, and many less than 10. Rolling stock leasing companies (ROSCOs), as well as operators, will expect to exploit these assets to the end of their useful life and will be reluctant to finance early replacement, even if the market can fund the £2 to £3 billion that entails.

At some point though, operators will look to replace, and it is right therefore to consider the likely options that may be available at that point, and to encourage the necessary research in the meantime. Given the small size of the UK market, this is likely to be dependent on synergies with the passenger market, or with other freight railways overseas. There are a number of potential options.

Chris Grayling’s favourite, hydrogen, shows promise for lightweight passenger markets, but there is no sense that it will ever have sufficient power for freight use. However, co-firing hydrogen and diesel may have some merit in reducing emissions, particularly if the passenger market has unlocked the necessary regulatory framework and infrastructure. In the American market there is an increasing use of liquefied natural gas (LNG), with shale gas readily available, and again this can be co-fired with diesel as well as alone. LNG, however, is still a fossil fuel, albeit a cleaner one, and there are implications for storage and, like hydrogen, the necessity to carry a large fuel tank reduces the payload of the train.

Road operators have researched a range of alternative fuels, including bio-methane and others. Again there seems to be no overwhelmingly obvious solution, although research continues. And of course, Elon Musk has produced a battery lorry, and there are battery vans with increasing range, though there remains a big gap between the power output of a 44-tonne truck and a 2,600-tonne train!

The most obvious solution is of course electric traction. Electrification is tried and tested, and as well as the environmental advantages there are operational benefits in improved acceleration and train length. Presently though, only around 8% of freight is electrically-hauled, and even where freight does operate under the wires there is increasing pressure to divert, for example onto the joint line or Felixstowe to Nuneaton routes. So the case for investment in new traction will be dependent on having enough wired routes to deliver the necessary economy of scale. Government sentiment to electrification is not good, but nonetheless, there is a good case for looking at what would be needed to reach a tipping point for investment in bi-modes, perhaps by electrifying the intermodal network. A possible freight railway electrification strategy is discussed in the article on page 56 of this issue.