Written question WQ83941
- Asked by
- Heledd FychanPlaid
- To be answered by
- Minister for Climate Change
- Tabled
- Due
- Answered
- Time to answer
- 6 days
Question
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?
Answer
Answered by Minister for Climate Change
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.