WAQ76935 (w) Tabled on 19/07/2018

What assessment has the Welsh Government made of the effectiveness of introducing 50 miles per hour speed limits, as well as other measures in five locations on Welsh roads, in improving air quality?

Answered by Cabinet Secretary for Economy and Transport | Answered on 31/07/2018

The Welsh Government has a legal duty to ensure compliance with the EU Ambient Air Quality Directive (2008/50/EC).  There are 5 locations on our motorway and trunk road network that exceed the Directive limit level for NO2 - 40 μg/m3, these are, the A494 at Deeside, the A483 near Wrexham, the M4 between junctions 41 and 42 (Port Talbot), the M4 between junctions 25 and 26 (Newport), and the A470 between Upper Boat and Pontypridd.  Detailed investigations, including modelling using the approach set out in the Welsh Transport Appraisal Guidance (WelTAG), are currently underway to establish the measures required to achieve compliance with the Directive as soon as possible.


The investigations and modelling undertaken to date have indicated that the implementation of 50 mph speed limits at each of the locations have the potential to bring immediate improvements to air quality and bring forward compliance with the Directive.  The effect of the temporary speed limits, implemented in June, on air quality will be closely monitored by road side testing.  The results will be fed into ongoing investigations and modelling, due to be completed by the end of August, to establish the final measure or measures likely to achieve compliance in the shortest possible time.


Our work has to comply with the Directive for the monitoring of air quality at the roadside of the trunk roads involved in the temporary speed limit scheme.  All of the study work was published with the air quality consultation document in April 2018 and we have further work on-going which will report at the end of August 2018.  The consultation closed on 19 June 2018 but the documents can still be accessed at the following link: https://beta.gov.wales/tackling-roadside-nitrogen-dioxide-concentrations-wales.


Based on the modelling data and the roadside air monitors, we have not taken the decision lightly to implement temporary speed limits.  Unfortunately, we need to act swiftly and report on the EU Directive progress and have legal obligations to meet by achieving compliance with legal limits in the shortest possible time.