Road transport emissions
Road transport is a major source of air pollution and associated health impacts as a leading source of nitrogen oxide (NOX) emissions — particularly in densely populated areas. NOX emissions also increase the levels of nitrogen dioxide (NO2) and particulate matter (PM2.5) in the atmosphere. These transport-induced changes in pollutant concentrations have a dramatic impact on public health. Emissions from this activity are close to the ground and often in densely populated regions.
Diesel boom in Europe and the UK
In the 1990s, road transport air pollution in Europe and the UK was aggravated by a boom in diesel vehicles, which was fuelled by European policymakers motivated by climate ambitions. At the time, the scientific consensus was that diesel vehicles emitted less carbon dioxide (CO2) than petrol vehicles and EU legislation led governments to incentivise diesel vehicles.
This expansion in the number of diesel vehicles had significant consequences for human health. Across Europe and the UK, emissions from diesel vehicles were responsible for 37% to 69% of transportation-attributable deaths, whereas non-diesel vehicles contributed only 5% to 14% in 2015.
Taking a closer look at diesel
Until 2017, official vehicle approval emissions testing was conducted exclusively in laboratories under standardised testing conditions. However, wider emissions testing had suggested for years that diesel vehicles were emitting significantly higher levels of pollutants on the road than during official laboratory tests. A cause of this was the use of ‘defeat devices’ – engine calibration technology that disables or reduces the effectiveness of emission control systems under normal driving conditions. Some defeat devices detect when vehicles are undergoing certification testing and temporarily reduce emissions in such settings to meet regulatory standards. However, the term ‘defeat device’ covers a much broader range of strategies that reduce emission controls in response to various vehicle signals, such as temperature, vehicle speed, and engine speed. Defeat devices are prohibited under both EU and UK law except for a few narrowly defined exceptions.
Dieselgate
In 2015, investigations by the International Council on Clean Transportation (ICCT) and West Virginia University‘s Center for Alternative Fuels Engines and Emissions (CAFEE) within the Statler College of Engineering, as well as the US Environmental Protection Agency (EPA), revealed that Volkswagen was using prohibited defeat devices. These prohibited defeat devices caused vehicles’ emission control systems to be switched on during laboratory testing conditions but then switched off under real-world driving conditions, leading to higher real-world NOX emissions. This became known as the ‘Dieselgate’ scandal.
Since the Dieselgate scandal, various legal developments have occurred that have sought to improve the regulation of NOX emissions from diesel vehicles and that have clarified that defeat devices can only be used in very narrow circumstances.
In 2023, the ICCT analysed official government emissions tests and real-world independent remote sensing data in the EU and UK. According to the ICCT’s analysis, vehicles with emissions above their ‘suspicious threshold’ are likely to be using prohibited defeat devices still to this day.
CREA health impact assessment (HIA)
This health impact assessment (HIA) analyses excess NOX emissions from diesel vehicles in the EU and UK between 2009 and 2040 and their health and economic impacts. More specifically, in this HIA, CREA calculates the air quality impacts of excess NOX emissions from diesel vehicles meeting Euro 5 and Euro 6 emissions standards approved before the introduction of the European Union’s Real Driving Emissions (RDE) test (which measures pollutants emitted in real-world driving conditions), that are considered likely to be using prohibited defeat devices that disable or reduce the effectiveness of emission control systems under normal driving conditions. Excess emissions are emissions that are suspiciously high (more than twice the legal limit) and likely linked to the use of prohibited defeat devices. This report also provides case studies exploring the impact of domestic emissions in the UK and France.
CREA HIA key findings
Across the EU and UK, excess emissions are projected to cause severe public health and economic consequences over the period of 2009 to 2040, including:
- 205,000 (123,000–356,000) premature deaths
- 152,000 (33,000–346,000) new cases of asthma in children
- 42,000 (15,000–80,000) years lived with chronic obstructive pulmonary disease (COPD)
- 24,000,000 (20,000,000–27,000,000) work absences (sick leave days)
- Associated economic burden from these health impacts of EUR 1.20 (0.72–2.07) trillion (in 2024 EUR).
Of these impacts, 124,000 (75,000–216,000) premature deaths and EUR 760 (460–1,320) billion in economic impacts have been caused between the period 2009–2024. If no additional measures are taken, 81,000 (48,000–140,000) premature deaths and EUR 430 (260–750) billion in economic impacts are projected between 2025–2040.
Immediate intervention by governments and auto manufacturers, such as investigating and recalling vehicles suspected to be using illegal defeat devices, could reduce future harm and lead to significant health and economic benefits.
| This report was commissioned by environmental law organisation ClientEarth and based on remote sensing data collated by the TRUE initiative and the International Council on Clean Transportation (ICCT), the organisation that broke the original Dieselgate scandal. The emissions covered are from a wide range of manufacturers from across the auto-industry. Find the full methodology in the report. |
