Above ground at a Cityringen station; Above ground at a Cityringen station;

What does emission-free rail look like?

All forms of rail, from trams to metros to long distance services, are energy intensive. As the global ambitions for energy efficiency reshape the sector, the focus is going to be on how rail owners and operators can reduce emissions from services, operations and supporting infrastructure.

To be meaningful, emission-free rail means ensuring that the whole life cycle of the rail sector works on a zero-emission basis – from traction (trains and how they are powered), to property (stations and depots) to infrastructure (all other elements of the railway necessary for trains to operate). Without an appropriate whole system life cycle analysis, any developments or investment decisions will address only part of the problem.

I believe there are four critical components to delivering emission-free rail:

  1. Leadership by governments and regulators;

  2. The right approach to technology,

  3. Innovation and trials;

  4. Finance and investment; and cross-industry collaboration.

Let’s look at them in turn.

Government leadership

With the state setting the agenda for public transport, a clear, consistent and predictable policy approach to emission-free rail by government, set at a national level, is critical to success. This includes a decarbonisation and emission target including clear dates for implementation and interim targets. A pathway to get there also needs to be identified, including metrics to measure success. This will mean working in partnership with the regulator to enable renewable energy and new technologies to be trialled and adopted to meet an emissions-free target. Incentives, policies and other government mechanisms to support innovation and trials will be important catalysts. High-profile government champions and communications campaigns will also be needed to support, communicate and deliver the government’s vision and pathway.

Technology, innovation and trials

If a transition to an emissions-free future is to be a practical reality by 2050 a total-system approach needs to be taken across rail, energy, water, waste and communications infrastructure. Specifically, interdependencies and technology availability need to be identified and tested to allow the transition to happen successfully.

Rail is already the most electrified mode of transport. Beyond bi-mode (diesel and electric-powered) options, several technologies need to be trialled and tested that offer zero tailpipe emissions on non-electrified tracks. The most innovative of such technologies are battery electric trains and hydrogen fuel cell trains. Both electrification and hydrogen will play a complementary role.

Battery electric trains with small batteries can be used on partially electrified lines, enabling costs to be reduced by not electrifying those portions of track that present most difficulties (such as bridges and tunnels). Hydrogen fuel cell technology can complement this for services requiring long-distance movement of large trains with low frequency network utilisation, a common set of conditions in rail freight.


Making the financial case for emission-free rail is critical. Those aspects that can be implemented straight away, through existing franchises, residual value mechanisms and asset transfers, will need immediate focus. New mechanisms and innovation outside the existing franchising and procurement models will also need to be identified. Quick wins and transitional measures that could happen now include radically reducing the emissions footprint of infrastructure through materials procurement and manufacturing practices that reduce embodied energy and waste.

Across rail operations there are many ways to lower emissions by improving efficiencies, for example by using building management systems, and using efficient appliances and lighting. Likewise, the core rail service and traction can both be improved by reducing the weight of carriages, using electric or hydrogen traction drives, applying eco-driving principles, and introducing regenerative braking and occupancy-driven heating and cooling services. Finally, ancillary signalling and other trackside equipment that permits better utilisation of the rail network, will reduce the embodied emissions per passenger km or per tonne km.


Everyone has an interest in an emission-free rail network; it will lead to better air quality and is central to tackling climate change. Given the complexities of meeting the global target by 2050, we need to view the reduction of energy use in the network as a core, collaborative goal. We will then need to transition to zero emission energy sources as they become more available and workable. Reducing energy use means fewer emissions, and exerts essential pressure on good design and operating practices, rather than relying on low emission sources to compensate for wasteful behaviours.

In every part of the world, emissions is a systemic challenge; a paradigm shift that requires new thinking and major investment. To achieve genuinely emission-free rail, everyone will need to play a part. This includes government, the rail industry, energy companies, stakeholders and communities working together and holding each other accountable to a shared vision. If we do that, meaningful progress is a realistic prospect.