A wnaiff y Gweinidog ddarparu'r data i gefnogi'r datganiad a gyhoeddwyd ar 27 Medi 2021, a oedd yn dweud bod y cynlluniau 50mya ar yr M4 a'r A470 eisoes wedi llwyddo i ostwng lefelau nitrogen deuocsid yn sylweddol mewn ardaloedd yr effeithiwyd arnynt hyd at 47 y cant?
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.