Source · Select Committees · Public Accounts Committee
Recommendation 18
18
Acknowledged
DfT explained to us that the national model ‘fills in the gaps’ in data collected...
Conclusion
DfT explained to us that the national model ‘fills in the gaps’ in data collected by its monitoring stations to create a kilometre by a kilometre map of air quality across the country, and forecasts to 2030.23 DfT also told us that the results of the national model are updated to account for local experience; for example, in Southampton the local authority found that the national model underestimated NO2 compared to the results of local monitoring, due to a different fleet mix than predicted, so the model was updated.24
Government Response Summary
The government agrees that the best available evidence is used to identify areas in exceedance and bring them into the programme, and that they continue to work with experts to improve the model and have set up a new monitoring network, and where monitoring identifies a potential breach, local authorities can share the information with the Joint Air Quality Unit.
Government Response
Acknowledged
HM Government
Acknowledged
2.1 The government agrees with the Committee’s recommendation Recommendation implemented 2.2 The government is satisfied that the best available evidence that meets the stringent requirements for assessing compliance with the annual mean Nitrogen Dioxide (NO ) limit 2 value under the Air Quality Standards Regulations (2010) (AQSR) has been used to identify areas in exceedance and bring them into the programme. 2.3 An uncertainty of around +/-30% is not unusual for a model of this scale and complexity, and assessments have demonstrated that the national model meets the uncertainty requirements for assessing compliance under the AQSR. The government continues to work with external experts to identify and implement further targeted improvements to the national model to ensure it uses the best available evidence and reflects the impact of local measures. The government has also set up a new monitoring network which has greatly increased the number of locations where compliance with NO limits is 2 assessed using measurements. This network is achieving lower levels of uncertainty (<15%) and has more than tripled the number of roadside measurements used in the NO compliance 2 assessment. Since both modelled and measured values contain uncertainties, the government cannot definitively guarantee that all areas of exceedance have been identified. 29 2.4 Where local authorities’ air quality monitoring identifies a potential NO breach, they 2 can share this evidence with the Joint Air Quality Unit. Whether a locally identified breach should be tackled through the NO programme or through the Local Air Quality Management 2 (LAQM) regime will depend on whether the monitoring data meets the specific siting and data quality requirements of the AQSR.