My first stage in working out where I can usefully contribute to making the railways more sustainable is to consider where our environmental impacts are coming from. Today I'll consider the impacts from normal operation of the railway, for example powering trains, buildings and encouraging passengers and freight to use more sustainable forms of transport.
The biggest impact here comes from the diesel or electrical power used by trains. Generally speaking, electric trains are more efficient and more powerful than diesel (except freight), so that provides part of the reason for electrifying several mainline routes for the first time over the next few years (Great Western, Midland Mainline and TransPennine). In other locations, the electrical supply is being upgraded to provide greater reliability. Low voltage electricity (ie 240v mains rather than 25kV overhead wires) is also required for associated infrastructure such as signalling, lighting, telecoms systems, and the motors and heaters for points. I would also include here power used at depots for everyday activities such as train cleaning, refuelling and maintenance.
However, the big question is: where does the electricity come from? I have so far seen no evidence of a large scale shift to renewable power sources, either through procuring energy differently or by directly owning the relevant wind farms or solar arrays. Part of the problem is that trains require a lot of power (either high voltage or high current) and it needs to be delivered in the correct phase in line with the national grid. Local power sources may struggle to do this without significant phase correction. Although I don't believe this is insurmountable, it may be better to start by dealing with the low voltage requirements first.
The railway network has plenty of buildings, from signal boxes and depots to engineering offices and stations, with a variety of different operators. Network Rail manages only 15 major stations and the remainder are run by train operating companies or local passenger transport executives. These could all be subject to the usual range of energy saving or local generation (wind or solar power) measures for workplaces and public circulation areas, from insulation to waste reduction, although stations have particular security problems which need to be taken into account.
Passengers and Freight
Where the railways work in conjunction with other transport modes to effectively replace cars (or planes) as a normal mode of transport, this can have significant environmental benefits in terms of carbon emissions. There are positive signs that this is starting to happen, but plenty more to do to ensure that trains are fully accessible to everyone (many stations are still working towards having full disabled access), fairly priced (!), reliable, frequent and in the places where people need to travel. For example, I fully support the campaign for a new station at the commuter village of Haxby in York, because this would significantly reduce traffic into the city centre from Haxby.
But it's not all good: long commutes by train still entail pretty significant carbon emissions, and so-called 'hypermobility', where people travel excessive distances to work, has some fairly damaging social consequences too (it is claimed that every 10 minutes added to your commute results on average in 10% less involvement in your local community). The real sustainable option is to live near where you work, so we need to redesign our cities and towns to make that possible for as many people as possible.
Freight is also a big issue, as most UK freight uses road transport rather than rail. Embarrassingly for environmental campaigners, hauling coal to coal-fired power stations represents a hefty proportion of UK rail freight... not very sustainable in the long run!