With the increasing recognition for cleaner air worldwide, various groups and governments have spearheaded campaigns to raise awareness about and take action to combat air pollution. One such example is the world’s first 24-hour Ultra Low Emission Zone (ULEZ) in central London, United Kingdom. The ULEZ was launched in April 2019 as a measure to reduce air pollution and improve air quality in the highly dense and congested city. 

About the ULEZ

The ULEZ in central London requires all vehicles entering or travelling within the region to meet stringent minimum emission standards or pay a charge. In order to further reduce the transport emissions and comply with the EU air quality standards, the mayor made the decision to expand the area that the ULEZ covers by 18 times (Fig 1) from 25 October 2021 onwards. The zone now covers 4 million people, which is roughly 44% of the city’s population. 

Fig 1: Expansion of the ULEZ in London (Source: BBC

Fig 2 depicts the severity of London’s air pollution before the implementation of the ULEZ. Evidently, the central region generates the highest levels of carbon emissions from vehicles, even surpassing the limit that was imposed. Therefore this warranted the imposition and expansion of the ULEZ. 

Fig 2: Spatial extent of the air pollution in London (Source: LAEI, 2016)

Compliance Rates

One of the goals of the ULEZ was to encourage the adoption of cleaner vehicles by motorists. The ULEZ requires that all vehicles entering the zone meet certain emissions standards, with penalties for those that do not comply. The monetary disincentive was intended to encourage motorists to invest in cleaner vehicles. 

According to a 2020 report published by the Greater London Authority, compliance has continued to grow through 2019 and 2020 for cars, vans and taxis despite the already high compliance rates. In 2019, the overall compliance rate was only 73%, but this figure rose to 85% at the end of 2020. 

 

Reduction in Emissions

Nitrogen dioxide (NO2) and particulate matter (PM10) are two of the most harmful pollutants emitted by diesel engines. A study published in Environmental Research Letters found that the ULEZ has led to a significant reduction in nitrogen dioxide levels by 28% and particulate matter levels by 37% in the first year of operation. 

Fig 3: Trends in monthly average NO2 concentrations in London with and
without ULEZ (Source: Mayor of London)

Fig 3 shows that in the scenario where ULEZ was implemented, the reductions in NO2 concentrations were much quicker and larger compared to without the ULEZ, for both inner and central London. Another report by the Mayor of London also stated that the area experienced an estimated 20% drop in average PM2.5 concentrations compared to 2017 levels. 

 

Other benefits of the ULEZ

Besides improving air quality levels and curbing high traffic flow in the region, ULEZ also brought numerous health benefits to the population. The same report estimated that it could save the NHS £5 billion in healthcare cost by protecting almost 300,000 Londoners from diseases attributable to air pollution, such as coronary heart disease, lung cancer and dementia. This means that people commuting to and from the region, as well as residents in the area will enjoy better air quality and higher standard of living in the long run.

 

Given the effectiveness of such a policy, cities elsewhere should also consider implementing a low emission zone particularly in the highly congested regions in order to ameliorate air pollution. However, this measure will only be successful if residents are willing to corporate and there must be presence of good law enforcement to deter people from breaking the rules.

 

Bibliography

Birkett, S. (2019, April 6). ULEZ is another important step on the path to banning diesel. Retrieved from Clean Air in London: https://cleanair.london/hot-topics/ulez-is-another-important-step-on-the-path-to-banning-diesel/

Edwards, T. (2021, October 25). ULEZ: London pollution charge zone not enough, campaigners say. Retrieved from BBC News: https://www.bbc.com/news/uk-england-london-59015375

Hajmohammadi, H., & Heydecker, B. (2022). Evaluation of air quality effects of the London ultra-low emission zone by state-space modelling. Atmospheric Pollution Research, 13(8): 101514.

Ma, L., Graham, D. J., & Stettler, M. E. (2021). Has the ultra low emission zone in London improved air quality? Environmental Research Letters, 16(12): 124001.

Mayor of London. (2020). CENTRAL LONDON ULTRA LOW EMISSION ZONE — 2020 REPORT. London: Greater London Authority.

Mayor of London. (2021). EXPANDED ULTRA LOW EMISSION ZONE – SIX MONTH REPORT. London: Greater London Authority.