Average speed cameras with green casings have been installed at four sections of Welsh trunk road where the speed limit was lowered from 70mph to 50mph in June 2018 to improve air quality.
The Welsh Government has published first-year monitoring results, which reveal reductions in nitrogen dioxide at all four locations and near a section of the M4 at Newport where the speed limit was reduced.
Poor compliance with the 50mph limit has resulted in average speed cameras being installed on the A470 at Pontypridd, M4 at Port Talbot (J41-J42), A483 at Wrexham and A494 in Deeside, Flintshire. Mean speeds through those sections ranged from 55mph to 58mph during the first year of reduced limits.
The cameras’ green casings denote they are specifically for environmental enforcement. The aim is that all-Wales safety camera partnership GoSafe will use them for enforcement, after a change in remit. GoSafe is currently tasked with enforcing road safety only.
Welsh transport minister Ken Skates said. “Speed compliance has been an issue over the past 12 months and, as a result, average speed cameras have been erected at four of the sites to monitor traffic speeds, while the M4 in Newport has spot cameras.”
The Government has made the 50mph limits permanent. Mr Skates said air quality was complicated and establishing cause and effect takes time.
“It is too early to make any firm conclusions on the effect the 50mph speed limit has had on the NO2 limits. Additional roadside data will be required before this improving air quality trend can be confirmed.”
The largest decrease in roadside NO2 was 13.8%, near the M4 at Port Talbot. The smallest was 3.9%, near the M4 at Newport – where the effect of reduced speed has probably been partially offset by increased traffic since the Severn Crossings tolls were abolished in December.