Signalling: The Carbon Challenge

Reducing carbon emissions and helping to negate the impact of global warming is a subject we hear about day in and day out. The obvious polluters are well known – road transport petrol and diesel engines, jet aircraft, power generation using fossil fuels – but what other products and processes generate carbon and what can we all do about it? A talk given to the Institution of Railway Signal Engineers (IRSE) London and South East section revealed some interesting evidence.

Rogue emissions

While collectively referred to as Carbon, what exactly are the gases causing global concern and why is it a problem now which did not seem to exist in the past? The principal gases are carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), and fluorinated gases. Of these, carbon dioxide is by far the most harmful and is causing 80% of the global warming effect.

Thousands of years ago, CO2 existed as 200 parts per million in the general atmosphere. With the coming of the industrial revolution this had risen to 300 ppm by 1910 and had risen again to 400 ppm in 2019, by which time the impact on climate change was being noticed. Extremes of weather were occurring, hotter and colder seasons, drier days, increased rainfall and rising sea levels. All of this have led to longer droughts, severe floods, shifting of seasons, and an overall temperature rise. The economic impact is significant and is worsening. The risk for transport is just one example but even population movement can result as the environment changes and islands disappear.

Although these gases occur naturally, the use of fossil fuels by humans is the biggest problem and, if the problem is to be reversed, the future behaviour and attitude of humans will be critical

Relativities and railways

Most us who work in the rail industry take pride in the perception that railways are a very efficient and environmentally friendly form of transport and as such, we are the ‘good guys’. In many ways this is true when compared to other industries, but do we risk a false sense of pride? Will this smug attitude lead to rail becoming complacent as to its carbon footprint with the risk that, in time, rail might be one of the worst offenders?

The much-loved concept of ‘electric trains good, diesel trains bad’ is an obvious headline but is it as simple as that? It is an economic fact that much of the UK’s rail network (and true of most other countries) will never be electrified. The advances being made in the automotive industry to produce electric vehicles that have greater range and faster charging times are there for all to see and one can visualise that in 10 to 15 years’ time, it will be the norm to buy an electric car. The challenge for heavy goods vehicles is greater and we shall have to see what will emerge.

Are the railways keeping up with this progressive shift and learning to use and adapt the emerging technology? The arguments for battery versus hydrogen continue without any sign of a clear resolution, while in the meantime the diesel fleet gets older with new diesel trains having to be built. Even the fashion for having hybrid trains, while maximising the use of electrification infrastructure where it exists, does not solve the bigger problem.

Root causes of carbon emission

While traction power is a dominant factor, there are other elements that impact on carbon emission, many of them relating to infrastructure. Some may view these as insignificant, but everything involved in engineering and operations needs to be considered. Looking at all aspects of a rail system, carbon generation can occur in virtually everything we do:

• Design: raw materials, transportation, manufacturing, construction and installation
• Usage: energy source, power consumption, accessibility,
• Maintenance: frequency of attention, fault rates, spares availability,
• Replacement and Refurbishment: equipment life expectancy, renewal with more efficient system, disposal, scrappage arrangements.

All of these will generate carbon to some degree; it might be a small amount but, when multiplied by the number of systems and equipment in a rail operation, it can mount up. All engineering disciplines are involved – civils, track, electrification, signalling, and telecommunications. A recent investigation by a team from London Underground revealed some surprising results for modern signalling systems.

Transport for London ambitions

While the UK government has an ambition to achieve net zero by 2050, in London an analysis has been conducted as to what would be needed to achieve net zero by 2030, just five years hence. A policy document has been prepared with the aim of reducing emissions across the life cycle of all assets and infrastructure. This cannot be done by TfL alone and needs cooperation from all suppliers and manufacturers.

A hierarchy of progression is based on four possibilities: build nothing, build less, build clever, build efficiently. Clearly, doing nothing will not be realistic in the longer term but do we sometimes instigate change for changes sake?

Modelling a test case

The Four Lines Modernisation (4LM) project to renew the signalling systems on the Metropolitan, Circle, District and Hammersmith & City lines has been used to model and measure how much carbon will be generated over the project lifespan. This takes into account the control centre located at Hammersmith, the equipment rooms, the trackside signalling equipment, and the radio transmission links. The associated modelling came up with a figure of 67,000 tonnes of carbon. A not inconsiderable figure – but how was it worked out and how does it stack up with other LU lines.

The trackside equipment involves cables and cable routes, radio masts and aerials, axle counters, signal heads, lineside cabinets, and equipment rooms. All these items were assembled into the modelling tool that took into account bills of quantities, manufacturer’s data, design documentation, energy consumption, and other data sources. A breakdown of the different components deduced the following:

• Equipment cabinet: 1322 kg.
• Base for an equipment cabinet: 200 kg.
• Aerial mast: 326 kg.
• Aerial mast base: 213 kg.
• Aerial: 5 kg.
• Cable termination: 43 kg.

All these are for individual items of which there are several hundred but, for a typical kilometre of route, the figure is 182 tonnes / km with cables and cable containments being 67% of this, access points and aerials being 16%, and the remainder being other elements of manufacture and installation. Note that fibre cables are much worse for carbon emissions than copper cable, primarily due to the energy intensity required in the manufacturing process.

The 4LM project uses Communications Based Train Control (CBTC) with radio as the link to the trains whereas earlier lines (Jubilee and Northern) use Transmission Based Train Control (TBTC) that employs track loops for communication to trains. The TBTC system has a figure of 164 tonnes / km, an 18% reduction. This is primarily because the radio equipment has a higher count in its manufacture and installation elements.

For the equipment rooms, the carbon figure is around 400 tonnes per room with energy consumption (primarily the use of electricity) being the biggest element. It begs the question as to whether racks of signalling equipment can be made more energy efficient. Similarly, the control centre at Hammersmith is calculated to produce 4,000kg of CO2, 75% of this being from the rack servers.

To rate the significance of all this, the traction power on the four electrified routes of the 4LM is estimated to produce 62,000 tonnes of CO2 per annum. The traction consumption is helped by the use of regenerative braking, DC sectionalisation, and coasting, all part of the automatic train operation intelligence.

The relevance of it all

So, how seriously should the results from the 4LM exercise be taken? In a wider extrapolation, what are the factors that might change the current thinking on carbon generation within rail infrastructure equipment and signalling in particular? On a fully electrified railway, it would seem that traction power will always be dominant as whilst the infrastructure elements are significant, many of them are one offs relating to design, manufacture, and installation.

Should signalling designs be changed for systems that are more carbon friendly? Should the 4LM project design have utilised track loops instead of radio? The answer is probably no since the advantages of a radio-based system are considerable: no track mounted cabling that makes life difficult for civil engineering maintenance; much easier to instigate changes when any reconfiguration of tracks takes place; less signalling equipment to be maintained.

What is clear is that signalling systems that increasingly impact on or even control how a train is driven (ETCS, CBTC, and suchlike), should maximise traction power efficiency thus reducing carbon generation.

To capitalise on all of this, infrastructure suppliers need to provide carbon data for their products, and this is already happening in the civils business. Signalling suppliers need to be more aware of the carbon factor with an associated upskilling of staff and signalling clients so that carbon is taken into account when considering purchasing options. Alignment to the objectives of 2030 and 2050 should be part of the mind set of all involved.

While much of what has been written here might be considered tiny in terms of the overall carbon challenge, one perhaps needs to be reminded of the Tesco advert ‘Every Little Helps’.

Thanks are extended to Aditya Gurtu who is a senior engineer in the London Underground Environment & Sustainability team and who had worked on the 4LM project. It was his presentation that inspired this article.

Image credit: istock.com/Adam Smigielski