Official Statistics

Transport and environment statistics: 2023

Published 19 October 2023

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 and air quality data is sourced from statistics from the Department for Energy Security and Net Zero, and the Department for Environment, Food and Rural Affairs, and are classed as Official Statistics. Journey emission comparisons are classed as Experimental Statistics. For more on these classifications, see the types of official statistics from the UK Statistics Authority.

The timeline of this publication series, and the previous years comparisons are drawn with, coincide with the coronavirus (COVID-19) related restrictions. As such, figures in this release may be affected and should be interpreted with caution.

Previous editions of Transport and environment statistics are avaliable.

Background information on some of the calculations in this report can be found in the supplementary materials, published alongside this report, including details of the journey emission comparisons and the limitations of the analysis. Data on journey emission comparisons can be found on our data table page, alongside data on air pollution from transport and greenhouse gases from transport.

Main findings

In 2021:

• domestic transport was responsible for emitting 109 MtCO2e (million tonnes of carbon dioxide equivalent) in the UK, a 10% increase from 2020, though emissions remain well below historic trends

• transport is the largest emitting sector of greenhouse gas (GHG) emissions, producing 26% of the UK’s total emissions in 2021 (427 MtCO2e)

• emissions from international aviation fell 10% from 2020 to 13.3 MtCO2e, following a fall in 2020 of 64%.

• on average, 304 kilotonnes of CO2e were emitted by transport in each local authority

• 32% of Nitrogen Oxides (NOX) emissions and 14% of particulate matter less than 2.5 micrometres across (PM2.5) emissions came from transport

These findings coincide with coronavirus (COVID-19) related restrictions, which should be considered when interpreting them, particularly when making comparisons to other years.

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

Greenhouse gases: Journey emission comparisons

This publication provides estimated GHG emissions from example journeys across the UK, based on different modes of transport in 2021. The data in this publication are provided with the intention of allowing users to compare the estimated emissions, produced via different modes of transport, using travel on four illustrative journeys across the UK in order to provide context. The estimated emissions from these example journeys are calculated using a consistent methodology across all modes to allow the GHG emissions per passenger to be compared. The data contained in this release are estimates and should not be taken as indicative of the actual emissions in these journeys or on routes similar to this as local conditions and circumstances will vary.

Using 2023 estimates of carbon emissions, we estimate that a petrol car journey from London to Glasgow emits approximately 4 times more CO2e per passenger than the equivalent journey by coach.

Emission-releasing activity considered here includes:

Direct emissions are emissions produced by the vehicle itself.

Indirect emissions 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 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, since aviation produces the largest indirect effects of all transport modes. These effects 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 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 almost twice as much CO2e per passenger than a journey by the average petrol car.

Plane journeys that transport many passengers emit very high levels of GHGs, require passengers to make additional journeys 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, using the example journey of Leeds to Belfast, car journeys must go further to reach the ferry terminal, and so cars end up emitting much greater GHG emissions. A journey can be more efficient in terms of emissions by being more direct, which is also a reason why our example train journeys show fewer estimated total emissions.

Background notes and limitations of data

The charts provided below are examples of how emissions from journeys can be estimated: they are not indicative of exact emissions for each instance of these journeys as conditions and circumstances will vary. The data can be used:

• to estimate emissions for an individual for a mode of transport used, and distance (not accounting for particular journey circumstances such as traffic or weather conditions)

• to compare estimated emissions when travelling via different modes of transport

This data cannot be used:

• to determine the precise total number or volume of greenhouse gas emissions from modes of transport or individuals

• to forecast emissions in future, or for specific time periods

• as a comparator with other data sources published on actual transport emissions

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 DESNZ 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 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.

The methodology used by the DfT for these journey emissions comparisons allows a consistent methodology to be applied across all modes of transport. We are aware that other methods for specific modes exists. However, the intention of these statistics is not to provide exact emissions for journeys but rather to enable users to compare emissions across modes on a consistent basis.

Further information, and guidance on how to develop such comparisons, can be found in the supplementary materials published alongside this report.

Figure 1: Indicative GHG emissions (KgCO2e) for a single passenger on example journeys, 2023 (Table ENV0701)

Description: this is a bar chart which shows an estimate of emissions in kilograms of CO2e from an example journey, Glasgow to London, in 2023. Plane: 175; Motorbike: 92; Petrol car: 90; Diesel car: 90; Train: 28; Electric car: 29; Coach: 22

Indirect Effects refer 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.

Description: this is a bar chart which shows an estimate of emissions in kilograms of CO2e from an example journey, Leeds to Belfast, in 2023. Plane: 102; Motorbike: 68; Petrol car: 66; Diesel car: 67; Train, 32; Electric car: 28; Coach: 23

Description: this is a bar chart which shows an estimate of emissions in kilograms of CO2e from an example journey, Manchester to Cardiff, in 2023. Motorbike: 44; Petrol car: 42; Diesel car: 43; Electric car: 14; Train: 12; Coach: 10

Description: this is a bar chart which shows an estimate of emissions in kilograms of CO2e from an example journey, Croydon to Wimbledon, in 2023. Black cab: 3.1; Motorbike: 1.7; Petrol car: 1.7; Diesel car: 1.7; London bus: 1.2; Electric car: 0.5; Tram: 0.4

Assumptions in estimating journey emissions

The following assumptions are made in calculating the above emissions:

• all calculations use the DESNZ conversion factors for 2023 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

Experimental statistics

Journey Emission Comparisons are badged as Experimental statistics. Users should be aware of the status and cautions of these series, which will vary for each statistic and will be explained within each publication. The statistics are new but still subject to testing in terms of their volatility and ability to meet customer needs. They do not meet the rigorous quality standards of National statistics, for example with respect to partial coverage. Further details on Experimental statistics can be found at the UK Statistics Authority.

Greenhouse gas emissions from transport: 2021

In 2021, the UK produced 427 MtCO2e of GHG emissions, up 5% from 2020. Transport was responsible for 109 MtCO2e.

Domestic transport emissions have decreased by 15% since 1990 while total UK domestic emissions fell by 48% in the same period.

Transport emissions were 13.6 MtCO2e lower than pre-pandemic levels in 2021 (11% lower than 2019).

Figure 2: Greenhouse gas emissions by sector, 2021 (DESNZ, 2023)

Description of figure 2: this is a line chart which shows the amount of domestic GHG emissions from each sector from 1990 to 2021. In 2016, emissions from the energy supply sector declined below emissions from the transport sector, and so from 2016 to 2021, transport has been the sector with the highest emissions. Most sectors have reduced emissions in this time period. Agriculture emissions include emissions from Land Use, Land Use Change and Forestry. Other emissions includes emissions from Public and Industrial Processes.

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 Energy Security and Net Zero (DESNZ) 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 2021.

Transport produced 26% of the UK’s total emissions in 2021, and remains the largest emitting sector in the UK. The majority (91%) of emissions from domestic transport came from road vehicles (100 MtCO2e). The biggest contributors to this were cars and taxis, which made up 52% of the emissions from domestic transport (57 MtCO2e), Heavy Goods Vehicles (HGVs) (20% of domestic transport emissions, 21 MtCO2e) and vans (17% of emissions, 18 MtCO2e).

Figure 3: Greenhouse gas emissions by sector, 2021, by proportion (DESNZ, 2023)

LULUCF refers to Land Use, Land-use Change and Forestry. Other combines public sector and Industrial processes. Figures may not sum to 100% due to rounding.

Description of figure 3: this is a doughnut chart which compares the proportions of domestic GHG emissions from each sector in 2021. Transport: 26%, Energy Supply: 20%, Business: 18%, Residential: 16%, Agriculture and LULUCF: 11%, Waste: 4%, Other: 4%.

Total domestic emissions rose by 20.2 MtCO2e in 2021. 50% of the increase in total domestic greenhouse gas emissions between 2020 and 2021 was from the increase in emissions from transport, as travelling restrictions during the COVID-19 pandemic were relaxed.

Of the 10.2 MtCO2e increase in emissions from transport from 2020 to 2021, 5.4 MtCO2e (53%) of this came from increased emissions from cars. This represents 27% of the increase in total domestic emissions for the year.

The 2020 to 2021 reporting period coincides with coronavirus restrictions, which will have impacted transport usage. This should be taken into consideration when making comparisons from this data.

Figure 4: Greenhouse gas emissions by transport mode, 1990, 2019, and 2021 (ENV0201)

Description of figure 4: this is a bar chart which compares the amount (in million tonnes of CO2 equivalent) of domestic GHG emissions from modes of transport in 1990, 2019, and 2021. The table below details the amounts:

Year	1990	2019	2021
Total domestic transport emissions	128	123	109
Emissions from cars and taxis	72	69	57
Emissions from HGVs	22	21	21
Emissions from vans	11	18	18
Emissions from shipping	8	6	5
Emissions from buses	5	3	3
Emissions from other	10	7	5
Emissions from international aviation	16	37	13
Emissions from international shipping	8	7	6

Emissions from other category: Comprises, in 2021: Rail, 1.6 Mt; domestic aviation, 0.7 Mt; motorcycles and mopeds, 0.5Mt; other transport, 1.7Mt; other road transport, 0.6Mt.

UK total transport emissions dropped by 15% overall from 1990 to 2021. Domestic transport emissions dropped by 15% while emissions from international aviation and shipping dropped by 17%. However, emissions from light vans increased by 62% during this same period. This may be due to the large increase in van usage since 1990.

The UK’s sixth Carbon Budget incorporated the UK’s share of international aviation and shipping emissions, to allow for these emissions to be accounted for consistently. With international emissions included, international aviation made 10% of the UK’s emissions from transport, and international shipping made 5%.

In 2021, emissions from international aviation were 13.3 MtCO2e, 10% lower than in 2020. This is the lowest annual figure since these records began, after an unprecedented fall in 2020 of 64%.

This was due to a continued fall in air traffic following the COVID-19 pandemic, with the number of international flights landing or taking off from the UK 9% lower in 2021 than in 2020, and 67% lower than in 2019 (AVI0102).

On the other hand, international shipping emissions have increased by 3% between 2020 and 2021, but they remain 15% lower than pre-pandemic levels and 23% lower than 1990 levels, as global trade and the 2009 recession have impacted this sector.

Provisional data (DESNZ, 2023) for the UK’s domestic GHG emissions from the transport sector for 2022 have been released. These estimates suggest that domestic transport carbon dioxide emissions have risen 3.8%, to 112.5 MtCO2e in 2022. This is 7.7% lower than in 2019, the most recent pre-pandemic year.

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 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 (ENV0201)

Mileage and fuel use

In 2021, cars made up 75% of the road vehicle miles travelled within the UK, but produced 57% of transport emissions, while HGVs made up a much smaller proportion of the vehicle miles (6%) and their emissions were disproportionately greater (21%). This is mainly because smaller vehicles are more fuel efficient, and HGVs typically travel longer distances with greater loads.

Figure 5: Emissions and mileage for cars, vans, HGVs and buses in 2021 (tables ENV0201 and TRA0101)

Description of figure 5: this is a bar chart which compares the proportion of vehicle miles done by road transport vehicles and the proportion of GHG emissions from those modes of transport, in 2021: Cars, 75% of mileage, 57% of road vehicle emissions; vans, 18% of mileage, 18% of emissions; HGVs, 6% of mileage, 21% of emissions; buses and coaches, 1% of mileage, 3% of emissions. Values may not sum to 100% due to rounding.

Between 1990 and 2021, new vehicles have generally been more fuel efficient. As a result, emissions do not rise as fast as mileage increases.

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. Despite this, the large increase in van usage since 1990 has meant a proportionate rise in emissions as a result, while cars and HGVs have reduced their emissions over the same time period.

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, df_VEH0220).

Figure 6: Change in mileage and emissions, 1990 to 2021 (tables ENV0201 and TRA0101)

Description of figure 6: this is a bar chart which compares the percentage change in road transport emissions from 1990 to 2021, and the percentage change in vehicle miles from those modes of transport, from 1990 to 2021. Cars showed a 6% increase in mileage from 1990 to 2021, and a 21% decrease in emissions in the same time period; HGVs, a 13% increase in mileage, and a 1% decrease in emissions; vans, a 119% increase in mileage with a 62% increase in emissions; buses and coaches, a 37% decrease in mileage and a 53% decrease in emissions.

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 2021 were 304 kilotonnnes of CO2e, though figure 7 illustrates the variation in emissions across local authorities.

High levels of emissions from transport were seen in urban areas such as Leeds and Birmingham, as well as Midlands areas such as Buckinghamshire and West Northamptonshire and towns around the Welsh border such as Cheshire.

Figure 7: CO2 emissions from transport by local authority, 2021 (DESNZ, 2023)

An interactive map of this data is available.

On average, local authorities emitted 304 kilotonnes of CO2 equivalent (kt CO2e) from transport in 2021. In the previous year (2020) the average emissions were 278 ktCO2e. This is an average increase of 9.4%.

Before the COVID-19 pandemic, in 2019, average transport emissions per local authority were 340 ktCO2e, thus in 2021 this average was 10.6% lower than pre-pandemic levels.

Figure 8: Percentage change in CO2 emissions from transport, 2020 to 2021 (DESNZ, 2023)

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 2021. 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).

In 2021, transport contributed a substantial portion of these air pollutants to the UK’s domestic total:

• 32% of nitrogen oxides
• 14% of PM2.5 emissions
• 12% of PM10 emissions

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: NOX emissions from vans, for example, are 3,000 tonnes greater than in 2010, while all other vehicle types have reduced their NOX emissions in this same time period.

Figure 9: Nitrogen oxides emitted by transport mode, 1990 to 2021 (table ENV0301)

Description of figure 9: this is a line chart which compares the emissions of nitrogen oxides from road transport from 1990 to 2021. In 1990, cars emitted 778 kilotonnes of NOX. This has declined to 95 kt. HGVs emitted around 232 kt in 1990, which has declined to 21 kt. Van emissions have decreased from 99 to 62 kt. All other road vehicle emissions also declined across this time period.

Most NOX emissions come from cars and taxis. Gradual reductions in NOX emissions among cars have been driven primarily by the introduction of legislative vehicle emission standards (for more detail on these standards, see table ENV302).

More recently these reductions have slowed with the exception of external shocks affecting transport, such as the COVID-19 pandemic or the 2008 to 2009 Great Recession. Following a 30% fall in NOX emissions from cars 2019-2020, emissions rose again by 5% in 2021, but remain 26% lower than in 2019.

Levels of particulate matter in the atmosphere remain high despite these improvements in air quality. PM2.5 from brake and tyre wear in 2021 is 18% above its total in 1990, and PM from road abrasion is 15% higher than in 1990. Road abrasion and brake and tyre wear together represent 84% of PM10 emissions from transport in 2021.

Figure 10: Air pollutants, from 1990 to 2021 (table ENV0301)

Description of figure 10: this is a bar chart which compares the emissions from transport of 8 air pollutants in 2021 to their level in 2010 and 1990. From 1990 to 2021, carbon monoxide (CO) has reduced 96%, nitrogen oxides have reduced 88%, particulate matter (< 10 micrometres) has reduced 64%, particulate matter (< 2.5 micrometres) has reduced 73%, Benzene has reduced 97%, Butadiene has reduced 98%, Lead has reduced 98%, and sulphur dioxide (SOX) has reduced 95%.

Official statistics

Official statistics are produced to high professional standards set out in the Code of Practice for Statistics. However, these statistics have not been assessed by the Office for Statistics Regulation. Details of ministers and officials who received pre-release access to these statistics up to 24 hours before release can be found in the pre-release access list.

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