Will the Minister provide the data to support the statement published 27 September 2021, stating that the 50mph schemes on the M4 and A470 have already been successful in significantly lowering the levels of nitrogen dioxide in affected areas by up to 47 per cent?
Air quality monitoring data collected using diffusion tubes at each location and adjusted using national bias adjustment factors, suggest a maximum reduction in annual mean NO2 concentrations of 18.5% on the A483 at Wrexham between 2018 and 2019 and a maximum reduction in annual mean NO2 concentrations of 46.3% on the A470 at Pontypridd between 2018 and 2020. However it should be noted that the latter period covers part of the coronavirus (Covid 19) pandemic period which had a significant impact on road traffic in Wales.
|
Annual mean NO2 concentrations (µg/m3) |
|||||
|
|
2018 Annual Mean |
2019 Annual Mean |
Percentage difference 2018 to 2019 |
2020 Annual Mean |
Percentage difference 2018 to 2020 |
|
A483 Wrexham - North Wales |
50.2 |
40.9 |
-18.5% |
27.5 |
-45.2% |
|
A494 Deeside - North Wales |
42.2 |
36.6 |
-13.3% |
26.5 |
-37.2% |
|
A470 Pontypridd - South Wales |
56.8 |
48.1 |
-15.3% |
30.5 |
-46.3% |
|
M4 Newport - South Wales |
63.5 |
59.2 |
-6.8% |
38.4 |
-39.5% |
|
M4 Port Talbot - South Wales |
48.4 |
43.0 |
-11.2% |
28.2 |
-41.7% |
Notes:
- 50mph speed limits have been in operation since June 2018
- In addition to confirm the beneficial effect of the speed limits on NO2 concentrations a longer run of data is required at each location and comparison with similar locations that are not subject to speed limits.