Train vs Car Carbon Emissions: Which Is Lower?

On the UK Government’s 2026 conversion factors, travelling by train produces about 81% less carbon than driving alone in an average petrol or diesel car. Against a solo electric car, however, the difference is negligible. Put two people in the electric car and its emissions per person are about half those of the average train journey.

That means there is no honest answer that works for every journey. If I were travelling alone in a petrol, diesel or hybrid car, I would take the train where the route and fare were reasonable. If two or more of us were travelling in an electric car, carbon would not be a reason to switch to rail. Shared petrol and diesel cars sit between those two cases, so the number of passengers and the actual route matter.

Train vs car emissions per kilometre

National rail produces 39.89g CO₂e per passenger-kilometre, compared with 207.51g for a solo petrol car and 214.11g for a solo diesel car.

Travel option	Emissions per person-km	Compared with national rail
National rail, average passenger	39.89g CO₂e	Baseline
Average petrol car, 1 person	207.51g CO₂e	Train 81% lower
Average petrol car, 2 people	103.76g CO₂e	Train 62% lower
Average petrol car, 4 people	51.88g CO₂e	Train 23% lower
Average diesel car, 1 person	214.11g CO₂e	Train 81% lower
Average hybrid car, 1 person	162.76g CO₂e	Train 75% lower
Average electric car, 1 person	40.01g CO₂e	Effectively level
Average electric car, 2 people	20.01g CO₂e	Car 50% lower

The comparison includes the energy used for the journey and the production and delivery of the fuel or electricity. It excludes vehicle manufacture and infrastructure for both train and car.

The important point in the table is not simply that trains are lower-carbon than cars. They are much lower-carbon than fossil-fuelled cars carrying one or two people, but an electric car changes the comparison completely.

How car occupancy changes the answer

Adding passengers reduces a car’s emissions per person because the vehicle’s total emissions are shared between everyone inside it. The national rail figure is already calculated per passenger, while the government car figures are published per vehicle.

For an average petrol car, the calculation works out at:

People in the car	Emissions per person-km	Result against rail
1	207.51g CO₂e	Train 81% lower
2	103.76g CO₂e	Train 62% lower
4	51.88g CO₂e	Train 23% lower
5	41.50g CO₂e	Roughly level

I would still regard rail as the clear lower-carbon choice against a petrol car carrying up to four people. It takes five people in an average five-seat petrol car to bring its emissions per person close to the national rail figure.

Rail Delivery Group uses 1.6 people as the average car occupancy in its leisure-travel comparisons. At that occupancy, an average petrol car produces about 129.69g CO₂e per person-kilometre, making rail 69% lower. That is useful when looking at travel across the country, but there is no reason to use it for a particular trip if you already know how many people will be in the car.

There is also a difference between taking an empty seat in a car that is going anyway and deciding whether the car should make the journey at all. The first question is about the extra emissions caused by one passenger. The second is about the emissions from the whole journey. Most people choosing between train and car are answering the second question, so the sensible calculation is to divide the vehicle emissions by the number of people who will actually travel.

Does the route change train and car emissions?

The route can change the result because road and rail distances differ, and because individual train services can perform much better or worse than the national rail average.

These examples use the 2026 national factors and rounded one-way distances. They are illustrations rather than measurements of a particular service or car.

Journey	Rail distance	Road distance	Train	Petrol car, 1 person	Petrol car, 2 people	Electric car, 1 person
London to Birmingham	181km	190km	7.2kg	39.4kg	19.7kg	7.6kg
London to Manchester	295km	295km	11.8kg	61.2kg	30.6kg	11.8kg
London to Edinburgh	632km	655km	25.2kg	135.9kg	68.0kg	26.2kg

For a solo petrol car, none of the modest differences between the road and railway routes comes close to cancelling out rail’s advantage. For a solo electric car, the two are so close that the distance to the station, the onward journey and the exact route can decide the result.

Route-specific rail data can make a much bigger difference. Rail Delivery Group’s Green Travel Data models the train type, fuel, route, carriages and passenger loading for about 6.5 million journeys. Its calculation for London to Edinburgh is 12.5kg CO₂e per passenger, while applying the national average to the assumed 632km rail distance gives 25.2kg.

That does not make the national figure wrong. It shows why I would use a route-specific figure when one is available. A busy electric intercity train should not be expected to match an average that also includes quieter diesel services. National Rail publishes a journey calculator based on the more detailed route data. View the calculator.

Is an electric car greener than a train?

An average electric car carrying one person is effectively level with national rail, while the same car carrying two people produces about 50% less carbon per person than the train.

The solo figures are 40.01g CO₂e per kilometre for the electric car and 39.89g for rail. A difference of 0.12g is too small to support a meaningful claim that either one is greener. It is well within the variation caused by the particular vehicle, train, route and electricity supply.

This is where a blanket statement such as “trains are greener than cars” stops being useful. It is broadly true for petrol, diesel and hybrid cars, particularly when the driver is alone. It is not true for a shared electric car on these figures.

Manufacturing is not included in either side of this journey comparison. Producing batteries, cars, trains, track and stations all creates emissions, but adding the manufacture of the electric car without also adding the train and its infrastructure would not produce a fairer answer. A decision about buying a car or building a railway needs a lifecycle assessment. A traveller deciding how to make one journey usually needs a like-for-like comparison of the journey itself.

Why do published train and car figures differ?

Published comparisons differ because they make different assumptions about passengers, routes and which emissions are included.

The first thing to check is the unit. A rail figure is normally given per passenger, whereas a car figure may be given for the whole vehicle. Unless the car figure is divided by its occupants, the comparison does not answer the traveller’s question.

The next issue is scope. Some calculations include only the fuel or electricity used during the journey. Others also include the emissions from producing and supplying that energy. Either approach can be useful, but the same boundary has to be used for both modes.

Finally, a national average and a route-specific result are answering slightly different questions. The national figure is suitable for a broad comparison or for reporting when the service is unknown. The route figure is better for choosing between two real journeys.

My test is straightforward: if a comparison does not state its unit, assumed car occupancy and emissions boundary, I would not rely on its percentage.

When should you take the train rather than the car?

For lower journey emissions, take the train instead of driving alone in a petrol, diesel or hybrid car. A shared electric car is generally lower than the national rail average, while shared petrol and diesel journeys need a closer look.

Your journey	Lower journey emissions
One person in an average petrol, diesel or hybrid car	Train
Two to four people in an average petrol or diesel car	Usually train, but compare the actual routes
One person in an average electric car	Too close for a national average to decide
Two or more people in an average electric car	Car, on the 2026 average factors
Any journey with reliable route-specific rail data	Use the route figure rather than the national rail average

That is how I would make the decision. I would not pay an unreasonable fare or turn a straightforward drive into a badly connected rail journey to chase a small theoretical saving. But the gap between rail and a solo fossil-fuelled car is not small. Where the train is a workable option, it is the obvious carbon choice.

The shared petrol or diesel car is the case worth calculating. Rail is likely to remain lower unless the car is close to full, but the margin may be narrow enough for the actual vehicle and route to matter.

If flying is another realistic option, see our comparisons of train vs plane carbon emissions and flying vs driving emissions.

How businesses should account for train and car travel

Businesses should report train and car journeys in Scope 3 Category 6, using the most specific reliable data available and applying a consistent emissions boundary.

For car travel, that means recording the fuel type, distance and number of occupants where possible. For rail, use route-specific data if it is dependable; otherwise use the national passenger-kilometre factor. The important thing is to record the assumptions rather than create a level of precision the travel data cannot support.

The practical order is to avoid journeys that are not needed, reduce emissions by choosing a lower-carbon mode, and then calculate what remains. Our guide to calculating a business carbon footprint explains how travel fits into the wider inventory.

Measure your business emissions

Funding climate action is a separate decision. It can support worthwhile work, but it does not remove the train journey or car journey from a company’s emissions inventory. You can see the carbon projects we work with and assess that contribution on its own terms.

Train vs car carbon emissions FAQs

Sources and methodology

This article uses government, industry and accounting sources checked on 2 September 2026.

• UK Government greenhouse gas conversion factors 2026, published by the Department for Energy Security and Net Zero. The calculations use the Business travel – land, WTT – passenger vehicles and travel – land, UK electricity for EVs and UK electricity transmission and distribution for EVs worksheets. View the publication.
• 2026 greenhouse gas conversion factors methodology report, used to check the passenger-car, electric-vehicle and national rail boundaries. View the methodology.
• Rail Delivery Group Green Travel Data, April 2026, used for route coverage, average car occupancy and the route-specific London to Edinburgh example. Its figures exclude well-to-tank emissions, so they should not be substituted directly into the national comparison table. View the publication.
• National Rail carbon calculator, which provides journey-specific comparisons based on Green Travel Data. View the calculator.
• GHG Protocol guidance for Scope 3 Category 6, used for the business-travel reporting context. View the guidance.

Exact 2026 conversion factors used:

Mode	Journey factor	Upstream factor	Total used
National rail, average passenger	30.92g	8.97g	39.89g CO₂e/passenger-km
Average petrol car	161.52g	45.99g	207.51g CO₂e/vehicle-km
Average diesel car	172.65g	41.46g	214.11g CO₂e/vehicle-km
Average hybrid car	129.61g	33.15g	162.76g CO₂e/vehicle-km
Average electric car	29.52g, including network losses	10.49g	40.01g CO₂e/vehicle-km

For cars carrying more than one person, the vehicle figure is divided by the number of occupants. The worked routes use the rounded rail and road distances shown in the table. Actual emissions vary with the vehicle, train, route, traffic, weather and driving style.