Official Statistics

Transport and environment statistics: Autumn 2021

Published 19 October 2021

About this release

This release presents statistics on the impact of transport on the environment, including greenhouse gas emissions from transport, and air quality. Greenhouse gas (GHG) and air quality data is drawn from National Statistics. Journey emission comparisons are classed as experimental statistics.

This supplemental release for 2021 provides updated journey emission comparisons and an update to 2019 air quality statistics, plus a new section on local authority carbon dioxide emissions. We invite feedback on the presentation and information supplied in this release.

Main findings

This publication provides estimated GHG emissions from example journeys across the UK, comparing different modes of transport, and presents statistics on GHG emissions and air pollution on transport. It also provides guidance for third parties on how to develop such comparisons (see supplementary materials).

Using 2021 estimates of carbon emissions, we estimate that a petrol car journey from London to Glasgow emits approximately 3.3 times more CO2e per passenger than the equivalent journey by train.

In 2019:

• domestic transport was responsible for emitting 122 MtCO2e (million tonnes of carbon dioxide equivalent). This was a 1.8% reduction in emissions from 2018
• transport emissions were 3% lower than the transport emissions in 2009
• international aviation emissions more than doubled, from 16 MtCO2e to 37 MtCO2e
• on average, 326.3 kilotonnes of CO2 were emitted by transport in each local authority
• 35% of Nitrogen Oxides (NOX) emissions and 13% of Particulate Matter (PM2.5) emissions came from transport. 12% of NOX emissions came from cars alone

Carbon Dioxide Equivalent (CO2e)

Different greenhouse gases, such as methane and nitrogen oxides have different impacts on the greenhouse gas effect. All gaseous emissions are converted to the amount of CO2 needed to create the same effect, and presented in this report as CO2e.

Greenhouse gases: Journey emission comparisons

The following analysis presents the carbon emissions of a set of representative journeys a person in the UK might take in 2021, via a wide range of transport modes, and their consequent emissions. See below for visualisation.

Direct emissions

These are emissions produced by the vehicle itself.

Indirect emissions

These are emissions produced by the extraction, refining, and transportation of the fuel used to power the vehicle. For electric vehicles, this includes the generation and transmission of electricity.

Indirect effects

These are complex effects produced by greenhouse gases interacting with the atmosphere, for example, contrails produced by planes in the atmosphere, which reflect sunlight. Due to their complexity, their GHG effect is uncertain and what is presented here is a central estimate. Indirect effects are only included in the calculation of air travel in our analysis. These are sometimes referred to as radiative forcing or RF.

Results

The statistical estimates developed using this method suggests that cars emit more GHGs per passenger mile than trains and coaches that convey more people, and so maximising the number of people per vehicle can reduce emissions per person.

For an example journey between London and Glasgow (see Figure 1), a journey via the average petrol car emits over 4 times more CO2e per passenger than the equivalent journey by coach, or 3.2 times more CO2e per passenger than an electric car (taking into account emissions from electricity generation and distribution).

The same journey by plane would emit over 7 times more CO2e per passenger than by coach, and 75% more CO2e per passenger than a journey by the average petrol car.

Plane journeys that transport many passengers emit very high levels of GHGs, require transport to and from the airport, and have uncertain climatic effects beyond this (for example, the reflection of sunlight on contrails), so can produce more GHG emissions than cars. However, for our Leeds to Belfast example, car journeys must go further to reach the ferry terminal, and so cars end up emitting comparable GHG emissions to the more direct plane journey. A journey can be more efficient in terms of emissions by being more direct, which is also a reason why our example train journeys emit less overall.

Caveats

Our methodology is under continuous development to improve accuracy and utility. However, we are aware of areas where estimates will be imprecise. In general, the Department for Business, Energy and Industrial Strategy (BEIS) conversion factors rely on the construction of averages from regular travel patterns, and so individual behaviour is likely to vary from this central estimate. For example, if a car is older than average, the journey may be more polluting. If the journey encounters less traffic than average, the journey may be less polluting. Likewise, the journeys the Department for Transport (DfT) have designed may not reflect every journey. For example, some journeys between the locations listed here may cover greater distances if different routes are used to avoid traffic, or refuel.

For more information, and for guidance on how to develop such comparisons, consult the supplementary materials published alongside this report.

Figure 1: Indicative GHG emissions (KGCO2e) for a single passenger, 2021 (Table ENV0701)

Indirect Effects in Figure 1 refers to the climatic effect of non-CO2 pollutants, such as water vapour, aerosols and nitrogen oxides. This chart reflects a central estimate of the journey’s non-CO2 effects, however this estimate is highly uncertain. Non-CO2 effects could be higher or lower.

All calculations use the BEIS conversion factors for 2021 and assume the journey is from the city centre. Trains use the national rail conversion factor which aggregates diesel and electric rail. Average engine size and 1.6 passengers assumed for diesel, electric and petrol cars. Flights assume all economy passengers and a drive via petrol car to the airport. Trams use a conversion factor shared with other metro rail networks, including some powered by non-electrified means. London buses use different conversion factors to other local buses, as they tend to have higher occupancy.

Greenhouse gas emissions from transport

In 2019, the UK produced 455 MtCO2e of GHG emissions. Transport was responsible for 122 MtCO2e. This is down 1.8% from 2018 despite a 2% increase in vehicle miles. Domestic transport emissions have decreased by 5% since 1990, while total UK domestic emissions fell 44% in the same period.

Figure 2: Greenhouse gas emissions by sector, 2019 (BEIS, 2020)

Transport became the largest emitting sector in 2016. This follows large decreases in energy emissions as the UK switched away from coal power and towards gas, while transport emissions have remained relatively static.

Data sources

The data we present on greenhouse gases comes from the Department for Business, Energy and Industrial Strategy (BEIS) GHG Inventory collected and modelled by the Ricardo Consortium (a third-party contractor). To calculate transport emissions, Ricardo combine data on fuel consumption with transport data to model emissions. It covers the period 1990 to 2019.

Transport produced 27% of the UK’s total emissions in 2019. Of this, the majority (91%) came from road transport vehicles (111 MtCO2e). The biggest contributors to this were cars and taxis, which made up 61% of the emissions from road transport (68 MtCO2e), followed by Heavy Goods Vehicles (HGVs) (18% of road transport emissions, 19.5 MtCO2e) and vans (17% of emissions, 19 MtCO2e).

Figure 3: Greenhouse gas emissions by sector, 2019, by proportion (BEIS, 2020)

Overall transport emissions increased until a peak in 2007, before decreasing year-on-year until 2013, when emissions started increasing again. Emissions only started declining again in 2018. 2019 transport emissions are equivalent to those of 2011.

Despite this overall stability, there have been significant changes in emissions within transport. Improved fuel efficiency of cars has generally seen emissions from cars decrease since the mid-2000s, from 72MtCO2e in 1990 to 68MtCO2e in 2019. Bus emissions have also decreased in this period, from 5 to 3MtCO2e between 1990 to 2019. However, van emissions have increased by 8 MtCO2e since 1990, a 65% increase, from 12 to 19MtCO2e. From 1990 to 2019, International Aviation emissions have more than doubled from 16 MtCO2e to 37 MtCO2e, a 138% increase.

Figure 4: Greenhouse gas emissions by transport mode, 1990 and 2019 (ENV0201)

Provisional data (BEIS, 2021) for the UK’s domestic GHG emissions from the transport sector for 2020 have been released. These data suggest that domestic transport carbon dioxide emissions have fallen 19.6% since 2019, to 97.1 million tonnes in 2020. This is associated with falls in transport usage during restrictions introduced in response to the COVID 19 pandemic. These estimates also suggest that domestic transport carbon dioxide emissions were 23% below the 1990 figure.

Domestic emissions

This report primarily focuses on UK domestic GHG emissions, which does not include international aviation and shipping. Emissions are estimated following the guidance set out by the Intergovernmental Panel on Climate Change (IPCC), as required for the UK’s submissions to the United Nations Framework Convention on Climate Change (UNFCCC) each year. Under this guidance, international aviation and shipping emissions are reported but not included within the UK total. The UK Government has recently announced that from Carbon Budget 6 (2033 to 2037), these emissions will be counted within the UK total.

This report focuses on ‘territorial’ emissions, which are those emitted within the UK’s borders. Alternative presentations, on a residency or a consumption basis, are also available in ENV0201.

Mileage and fuel use

In 2019, cars made up 79% of the road vehicle miles travelled within the UK, but produced 55% of transport emissions, while HGVs made up a much smaller proportion of the vehicle miles (5%) and their emissions were disproportionately greater (16%). This is mainly because smaller vehicles are more fuel efficient.

Figure 5: Emissions and mileage for cars, vans, HGVs and buses in 2019 (Tables ENV0201 and TRA0101)

Between 1990 and 2019, new vehicles have generally been more fuel efficient. As a result, emissions tend to decrease at a slower rate than total vehicle miles. However, this effect is stronger for some modes than for others.

Fuel efficiency gains in HGVs have been offset by an increase in the proportion of larger/heavier HGVs amongst new registrations (DfT, VEH0506). In addition, new car fuel efficiency has been decreasing since 2016 after a period of growth. This is largely driven by an increase in the proportion of SUVs and other large vehicles amongst new car registrations (DfT, VEH0220).

Average new van fuel efficiency has increased in recent years because of the legislation of 2016 that ensures that all new vans must comply with Euro 6.

Figure 6: Change in mileage and emissions, 1990 to 2019 (Tables ENV0201 and TRA0101)

CO2 Emissions from transport by local authority

CO2 emissions from transport are unevenly distributed throughout the UK. Average transport emissions for a UK local authority in 2019 were 326.3 kilotonnes of CO2, though figure 5 illustrates the variation in emissions across local authorities. High levels of emissions can be found in urban areas such as Leeds and Birmingham as well as more rural areas such as Cornwall, Wiltshire and Shropshire.

Figure 7: CO2 emissions from transport by local authority, 2019 (BEIS, 2021)

Almost all local authorities have seen reductions in emissions from transport compared with 2005, by an average of 9%. This reduction is particularly concentrated in dense urban areas, with the greatest reductions coming in local authorities in London boroughs such as Camden and Westminster, as well as in areas in Scotland such as East Renfrewshire and Inverclyde.

Figure 8: Percentage change in CO2 emissions from transport, 2005 to 2019 (BEIS, 2021)

These data display vehicle emissions from roads, railways, inland waterways, and emissions from aircraft support vehicles. Readers should note that there is variation within local authorities, for example large motorways, which can skew overall presentation. Those emissions excluded are aviation, shipping and military transport for which there is no obvious basis for allocation to local areas.

Air pollution

Data sources

Air pollution figures for the UK are measured by the National Atmospheric Emissions Inventory (NAEI). Data here covers the period of 1990 to 2019. Unlike GHG emissions expressed as CO2e, there is no agreed way of comparing relative effects of different air pollutions. As a result, this report does not include a summed total of all air pollutants. Policies and targets to reduce air pollution are set out in the Clean Air Strategy (2019).

Transport vehicles also emit gases or other substances which don’t have a significant greenhouse gas effect, but do have significant health consequences. The most significant air pollutants from the transport sector are nitrogen oxides (NOx) and particulate matter (PM).

Transport contributed a substantial portion of these air pollutants to the UK’s domestic total:

• 34% of NOx emissions
• 13% of PM2.5 emissions
• 11% of PM10 emissions

came from transport in 2019.

Air pollutants from transport have decreased since 1990, largely because newer vehicles emit less nitrogen oxides and methane. However, emissions are also dependent on vehicle type: in the decade 2009 to 2019, cars reduced NOx emissions by 19% despite increases in car mileage, while total NOx emitted by vans increased by 59% alongside increases in van mileage.

Figure 9: Nitrogen Oxides emitted by transport mode, 1990 to 2019 (Table ENV0301)

This reduction in NOx emissions among cars is driven primarily by the introduction of legislative vehicle emission standards (for more detail on these standards, see ENV0302.

By contrast, particulate matter (2.5 and 10) has proved more difficult to reduce. PM from brake and tyre wear has increased by 35% since 1990, and PM from road abrasion has increased by 34% in the same period. These 2 sources together represent 61% of PM10 emissions from transport in 2019 (see figure 10).

Figure 10: Air pollutants, from 1990 to 2019 (Table ENV0301)

Electric vehicles and charging devices

Information on this topic is now included in the quarterly chargepoints publication.

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Transport energy and environment statistics

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