Paving the Way for Green Travel: Rail Beats Air with 13x Lower Carbon Emissions, Reveals New Calculator

The Green Travel Pledge methodology pioneered by Thrust Carbon on behalf of the rail industry, demonstrates the critical importance of rail as a business travel medium

Written by Cameron Kelly on 30 June, 2023

Businesses rely on good data to make the right travel decisions

65% of Global Business Travel Association (GBTA) members agree that quantifying carbon emissions reduction opportunities is the most challenging aspect of addressing sustainability. As we work to enhance the data that goes into reporting carbon emissions, net zero goals become more achievable. This couldn’t be more true for Great Britain’s rail industry, where the methodology we’ve built with the Rail Delivery Group, Great British Railways Transition Team, and Fabrik, is showing that rail travel creates 10 times less carbon emissions per passenger than the equivalent car journey and 13 times less than travelling by plane.

As businesses become increasingly conscious of their environmental impact, they are beginning to explore ways to make business travel more sustainable. When data accuracy improves, travel choices become clearer.

Introducing the Green Travel Pledge rail carbon calculator

As experts in sustainability intelligence, Thrust Carbon was chosen to collaborate with the Rail Delivery Group, data partners Fabrik and the wider rail industry to develop a new methodology for calculating rail journey emissions with accurate and reliable data. The work is part of the rail industry’s Green Travel Pledge, which is a commitment to empower business travellers to make more informed choices on environmentally-friendly travel modes.

The Green Travel Pledge rail carbon calculator offers a detailed, route-specific estimation that takes into account the intricacies and diversity of rail operations. This advanced perspective combines seven rail data sets which have never before been utilised together to measure the carbon footprint of rail travel.

The rail carbon calculator reports emissions based on energy consumption metrics specific to different engine types, actual travel distance (including the literal twists and turns of the rail route, rather than a straight distance between start and end points), carriage count, class type, and crucially, passenger load.

Advancing the foundation of Defra

Although the UK Government's Greenhouse Gas Conversion Factors for Company Reporting, developed by Defra, has served as a valuable framework for measuring rail transport, the Defra methodology relies on dividing the total energy consumed by the UK rail network by the total distance travelled. This approach results in a generalised average emissions factor. While this methodology was a pioneering step in rail emissions accounting, it inherently fails to capture the nuanced variations across different rail routes, engine types, and passenger loads.

Recognising this limitation, we have collaborated with our partners to take it a step further. Our methodology elevates emissions estimation to the highest level of precision.

The preliminary results

We’re proud to release the preliminary results for journeys on the electrified rail route from London King’s Cross to Edinburgh Waverley Station.

The table below shows the increased accuracy of our methodology compared to the Defra average for the specific route from London King’s Cross to Edinburgh Waverley:


Mode of Transport


Emissions per Passenger (KGCO2e)

London to Edinburgh


Thrust Carbon


London to Edinburgh




London to Edinburgh




London to Edinburgh




London to Endinburgh rail vs air

Our methodology has produced a figure of 12.5kg CO2e for the London to Edinburgh route, which is significantly lower than the Defra estimate for the same journey. Moreover, this notable reduction in calculated emissions highlights the environmental benefits of selecting rail travel over air travel. Our findings demonstrate that the carbon footprint of this rail journey is only a fraction of the 165.1kg CO2e associated with flying the same route using the Defra method. This clear comparison emphasises the potential for businesses to make a substantial contribution to their sustainability goals by choosing rail travel.

The following table shows how the methodology used for the rail carbon calculator compares to Defra’s approach:



Green Travel Pledge

1. Engine Type



2. Energy Usage

Average of GB Rail Network

Yes, specific to the locomotive

3. Distance Travelled

Total of GB Rail Network

Yes, specific to the

4a. Number of Carriages (Standard Class)



4b. Number of Carriages
(First Class)



5. Train Capacity


Yes, based on load influence

6a. Load
(Standard Class)



6b. Load
(First Class)



7a. Volume of trains



7b. Schedule Timetable



* We took an average based on modelling of expected passengers from ticket sales between two points per weekday over the last 6 months

** We took the average number of direct trains between London and Edinburgh per week day

*** Used to inform train volumes (input 7a)

Rail comparison table

Graph showing the data Green Travel Pledge methodology considers vs DEFRA

A closer look at the rail carbon calculator methodology

Here's how our prototype methodology functions:

  1. Energy Consumption Metrics: Rather than using general averages, we determine the energy consumed per kilometre by specific engine types on the electrified route from London to Edinburgh. This approach provides us with a more accurate representation of energy usage and resultant emissions.

  2. Conversion to Carbon Emissions: By employing the UK energy grid emissions factor and the UK energy Transmission & Distribution (T&D) emissions factor, we convert energy usage into CO2 emissions, thereby establishing a link between energy consumption and its environmental consequences.

  3. Allocation of Emissions Among Carriages: Our prototype ensures precise allocation of emissions between standard and first-class carriages based on their layout (with seating usually spaced out more in first-class) – a detail overlooked by the Defra methodology.

  4. Per Passenger Emissions Estimation: This aspect holds particular importance. We calculate emissions per passenger for each carriage type, taking into account the average passenger load. This means we consider both peak and off-peak travel times, acknowledging that the carbon footprint per passenger decreases as passenger numbers increase. This load factor ensures an accurate reflection of the impact of passenger occupancy on carbon emissions.

  5. Comprehensive Emissions Evaluation: Our methodology culminates in calculating a weighted average of emissions per passenger kilometre, providing us with an average emission rate for the specific electrified route.

Boundless opportunity

The precision of this methodology will not only provide businesses with more accurate emission data but also enable them to make informed, environmentally conscious travel decisions. This feature aligns with the anticipated modal shift from air to rail, highlighted in the ITM Buyer Priorities Survey 2023.

The pivotal role that rail travel can play in achieving sustainability objectives cannot be overstated. To fully leverage this potential, businesses need access to transparent, accurate emissions data - a need that is directly addressed by Green Travel Pledge carbon calculations. This precise estimation of rail travel emissions gives organisations a comprehensive understanding of the environmental impact of their travel choices.

In developing this prototype, we believe we are at the forefront globally of rail emissions estimation techniques. This prototype, however, represents more than just a tool—it's an inaugural step towards a future where businesses can better align their travel policies with sustainability objectives. Later this year, we will be working with the rail industry to make carbon emission data available to businesses for all rail routes across Britain.

Thrust Carbon is ready to support your goals

If you’re interested in hearing more about this groundbreaking venture, or how your organisation can effectively navigate the intricate landscape of travel emissions and make notable contributions to sustainability initiatives, please reach out to our Thrust Advisory lead:

Our collective effort is a stride towards a world where every journey contributes to a greener future. We are ready to work with you to make every journey count. Are you?

For more information, reach out to our Thrust Advisory team or visit

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