Residential Air Quality Assessment, Dartford

The challenge

The proposed residential development falls within Dartford, an area which suffers from elevated levels of air pollution, primarily due to high levels of traffic. Dartford Borough Council has declared four Air Quality Management Areas (AQMA)s; the proposed development site is adjacent to an AQMA at the Dartford town centre and approach roads. Another committed residential development which is expected to generate increased traffic levels, is located within the vicinity of the proposed development.

The solution

The dispersion modelling tool ADMS-Roads was used, in combination with local meteorological data and traffic data to predict nitrogen dioxide (NO₂) and particulate matter (PM₁₀) concentrations at the site. This allowed for the following future air quality scenarios to be modelled:

• Should no developments go ahead
• The nearby residential development goes ahead
• Both the nearby residential development and the residential development in question go ahead

These scenarios were run using three different methods of estimating emissions released by the vehicle fleet:

1. Maintaining Defra emission factor toolkit (EFT) vehicle fleet emission factors and background concentrations from a recent year, i.e. assuming no improvements to the fleet by the time the development is completed . This is a worst-case scenario.
2. Using EFT emission factors and background concentrations for the year the development is expected to be completed, i.e. assuming Defra’s predicted improvements in the vehicle fleet by this year.
3. Vehicle fleet emission factors for the future year from the Calculator Using Realistic Emissions for Diesels (CURED) v3A model combined with an updated background CURED background concentration that take a more pessimistic view than the Defra EFT on the performance of post 2019 diesel cars and vans. It is considered to be a worst-case sensitivity test. It is worth noting that the CURED model only includes NO₂; PM₁₀ is not estimated.

The result

The results of the assessment indicate that the annual mean NO₂ and PM₁₀ objective level concentrations will not be exceeded at the development site or on nearby residential roads that will experience increases in traffic due to the cumulative impact of both this development and the nearby development. Therefore, no specific mitigation is required. However, the developer was encouraged to consider measures such as providing secure and covered cycle storage, implementing a travel plan, and installing electric charging points, to reduce the traffic emissions arising from the development.

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