Modelling of air quality in the LTNs is being completed by independent consultancy: Cambridge Environmental Research Consultants Ltd (CERC)
The impact of each LTN on air quality has been assessed through air quality modelling. Two key pollutants have been modelled; Nitrogen Dioxide (NO2) and Particulate Matter (PM10 and 2.5).
The modelling was carried out in two stages:The first stage considered the baseline air quality conditions To establish the air quality baseline, traffic flow data was provided for each Automatic Traffic Counter (ATC) site in the scheme areas for 2019, based on historic traffic data. The second stage considered the impact on air quality with and without the LTN schemes. The model went through a verification process to make sure the model aligned with real-world monitoring to generate a robust model set-up. CERC modelled the impact on sensitive locations: schools, hospitals, care homes and other educational establishments.
To understand the air quality impacts of the LTNs it is important to know how air quality is measured and what is considered poor air quality:Both NO2 and PM are measured in micrograms per cubic meter of air (µg/m3). NO2 is subject to an annual average legal limit, which is 40µg/m3, and a short-term hourly average limit of 200 µg/m3, which cannot be exceeded more than 18 times per year. The legal annual average limit for PM2.5 is 25µg/m3. However the World Health Organisation advise that there is no safe minimum limit for PM2.5
This air quality assessment is more detailed and comprehensive than the typical approach used across the industry.
Air quality in London:Air quality in London is improving five times quicker than elsewhere in the UK. London specific policies like the Ultra Low Emission Zone have delivered really big improvements in air quality. The Ultra Low Emission Zone is currently operating in central London. It will expand to include all roads within the north and south circular roads in October 2021, with big improvements to air quality anticipated across a much wider area.
Results of air quality modelling:The LTN is expected to have had some localised impact on air quality, with some roads likely benefiting such as Railton Road, Dulwich Road, the western part of Shakespeare Road and the eastern part of Coldharbour Lane and others seeing a small modelled increase in emissions such as the western part of Coldharbour Lane near Atlantic Road. Across the Railton LTN there are no modelled exceedances of the relevant air quality standards for NO2, PM10 or PM2.5 at any sensitive location sites both within the LTN and on the boundary of the LTN. This includes St Judes’s C of E school, Evelyn Grace Academy and Effra Nursery School within the LTN, and Michael Tippet School and Jessop Primary School on the boundary of the LTN. Where NO2 levels are likely to have increased, that increase is expected to be mitigated by the expansion of the Ultra Low Emission Zone in October. ULEZ is expected to mean that all sites, including on boundary roads, have improved air quality compared to before the LTN was introduced. Air quality at 6 school locations were modelled specifically to understand the likely impact at sensitive locations.
Above: difference plot for NO2 based on impact descriptor coloured by EPUK IAQM significance criteria, Railton LTN
Since the Stage 1 monitoring report was published we have received 93 pollution related emails.
Benefits noted:Perceived reduction in air pollution particularly on Railton Road. Perceived reduction in noise pollution.
Concerns noted:Perceived increase in noise pollution. Perceived increase in air pollution. Concerns were raised regarding air pollution on roads such as Coldharbour Lane, Dulwich Road, St Matthew’s Roundabout, Milkwood Lane and Effra Road.