Summary:
Assessment of Air Quality Measures
The Deliverable details how the Emerald air quality modelling system can be used to support Ireland’s local authorities to prepare air quality plans and assess local measures aimed at reducing air pollution levels in their local jurisdictions.
As part of the recent (2023) National Demand Management Strategy, studies are being carried out to assess optimal traffic congestion reduction measures for Dublin. Together with the National Transport Authority (NTA) and the Department of the Environment, Climate and Communications (DECC), it was decided to model the impact of the proposed 2030 ‘Low Emission Zone (LEZ) package for Dublin.
Traffic emissions data for the East Regional Model (ERM) in 2030, under two scenarios, low growth (ADH) and high growth (ADI) was provided by the NTA. Based on this data, the impact on NO2 concentrations was modelled. Other input parameters included background concentrations for 2030, based on the With Existing Measures (WEM) scenario, to determine the chemical equilibrium between Nitrogen Oxides (NOX) and Ozone(O3), and meteorological data (wind speed and direction) for 2021. No other emissions are considered.
Figure 1 in the report shows the concentration difference for annual mean NO2 levels between the ADH and the ADI scenarios (with green colours indicating locations where the ADI scenario provides lower concentrations). The results indicate that for a large part of the modelled domain, the differences are limited, being smaller than 0.2 µg/m³. In Dublin City Centre and in a wide band around the M50 motorway, the concentrations increase moderately (between 0.2 and 0.6 µg/m³). Larger differences are observed only very close to the main roads and in some busy street canyons in the city centre. At almost all locations, the concentration difference is smaller than 2 µg/m³.
The methodology demonstrates that, in general, as long as the data format of the NTA's network is being used, it should be relatively easy to couple city-scale emissions projections from similar studies to the Emerald model chain, although some gap filling may be required.