The Ultra-Low Emission Zone (ULEZ) - an overview

Changes to the ULEZ

The Greater London Authority expects the expansion to enable five million more Londoners to breathe cleaner air, with a £110m scrappage scheme being provided to help those eligible to replace their old vehicles.

The ULEZ charge uses the European standards (Euro standards) which set limits on emissions of pollutants to air. Previously, the charge applied to Euro 3 motorcycles, mopeds, motorised tricycles and quadricycles; Euro 4 petrol cars, vans, minibuses and other specialist vehicles; and Euro 6 diesel cars, vans and minibuses and other specialist vehicles.

How does this change affect Air Quality Assessments?

The expansion of the ULEZ will affect the way air quality impacts across London are assessed. Careful consideration will be required to establish appropriate input data and to interpret the results of air quality assessments. Some of the areas that will need to be considered include:

• Background Concentrations - Historically, background traffic-related pollutant concentrations in the UK have reduced over time, as cleaner vehicles become an increasing proportion of the fleet. The expanded ULEZ may lead to a step change in background concentrations. Using present-day measurements as an indication of the future baseline concentrations may be overly conservative. We'll be monitoring the results of annual air quality status reports produced by local authorities to determine how background concentrations change once the expanded ULEZ is implemented.
• Emissions – Defra’s Emissions Factor Toolkit provides forecasts. The current toolkit considers the ULEZ in central London, but doesn't include the impacts associated with the expansion in 2021 or the expansion in 2023. With the expected benefits of the expanded ULEZ, predictions using the current toolkit may be too high. A conservative approach may be useful for some projects, but if the future impacts are over-estimated it could mean that significant effects are incorrectly predicted, leading to the potential implementation of unnecessary mitigation. We'll use professional judgement to justify any divergence from the emissions factors drawn from the toolkit.
• Traffic - Traffic flows and fleet compositions extrapolated from pre-ULEZ expansion data may not be representative, either within or on the outside periphery of the expanded ULEZ. In some cases, it may be necessary to undertake sensitivity tests, where we'll work with transport consultants to build appropriate scenarios to model.
• Construction Dust - During the construction phase of a development, HGVs will be required to bring materials in and out of the construction site. The expansion of the ULEZ may influence the number of trips and the routes taken. This may affect the nature and scale of measures recommended to control and mitigate the risk of tracked out dust during construction works. Working with our clients, we'll determine the most likely routes that will be used by construction vehicles.

How can we help?

As part of our commitment to producing market-leading air quality assessments for developers submitting planning applications, we'll continue to identify any factors which introduce uncertainty in our assessments, including those surrounding the expansion of the ULEZ. We'll exercise professional judgement on the implications for the assessment findings and this may include the use of sensitivity tests.