Y Pwyllgor Deisebau | 15 Ionawr 2019
 Petitions Committee | 15 January 2019
 ,P-05-853 No to any closure of junction 41 




Research Briefing:

Petition number: P-05-853

Petition title: No to any Closure of Junction 41

Text of petition:  Calls on the Welsh Government to reject any proposal to close junction 41 of the M4.

A report by WSP to Welsh Government published in September 2018 which considers measures on the Welsh Government motorway and trunk road network for Nitrogen Dioxide reduction includes a proposal to close Junction 41 westbound on slip as a measure to reduce roadside emissions on the M4 between junction 41 and junction 42. This will only increase emissions of Nitrogen Dioxide on local roads and have a greater impact upon local people particularly children.


The Welsh Government is the statutory highway authority for the Welsh trunk road and motorway network – including the M4.

In 2014-15 the Welsh Government trialled closure of the westbound on-slip at Junction 41 of the M4 at Port Talbot in an effort to reduce congestion.  The trial closure period ended in May 2015. However consideration of future options for the junction continued

In October 2016 the then Cabinet Secretary for Economy and Infrastructure indicated that he had “decided not to proceed with further consideration of slip road closures at Port Talbot at this time”.

In February 2018, in a case brought by the environmental group ClientEarth, the High Court ruled that the Welsh Government had failed to develop adequate plans to meet EU targets to cut air pollution. The ruling in the case, which also included the UK Government, placed a legal obligation on the Welsh Government to draft a plan by the end of April 2018, and have a final plan in place by 31 July 2018, to improve air quality across Wales in line with EU law. However, in July 2018, the Welsh Government applied to the High Court for an extension which was granted.  The Welsh Government was required to publish the new plan by 30 November 2018.

On 24 April 2018, the then Minister for Environment, Hannah Blythyn, made a Plenary statement setting out a range of measures to address air quality issues.  These included the introduction of 50mph speed limits on five stretches of the trunk road and motorway network, including the M4 between junctions 41 and 42.

The trials were intended to reduce nitrogen dioxide (NO2) concentrations where these exceed requirements set out in the EU Ambient Air Quality Directive and the associated Air Quality Standards (Wales) Regulations 2010.  The temporary 50mph zones were implemented from June 2018. When the then Cabinet Secretary for Economy and Transport appeared before the Climate Change, Environment and Rural Affairs Committee for scrutiny in November 2018, he told the Committee that the Welsh Government is due to report on the effectiveness of the 50mph zones in improving air quality in early 2019.

The Welsh Government launched a consultation on tackling roadside nitrogen dioxide concentrations in Wales in September 2018.  The Welsh Transport Appraisal Guidance (WelTAG) stage 3 assessment for Junction 41-42 (PDF 2MB), published as part of this consultation, is the report by WSP referred to by the petitioners. WelTAG stage 3 is a full business case and is used to make a detailed assessment of preferred measures to inform a final implementation decision. 

The report set out seven “hard measures[1]” to be appraised at stage 3, including three which involved junction closure: 

§    Junction closure option A (J41 Eastbound on-slip), plus 50mph Speed Limit;

§    Junction closure option B (J41 Westbound on-slip), plus 50mph Speed Limit; and

§    Junction closure option C (J41 Eastbound and Westbound on-slips), plus 50mph Speed Limit.

On 29 November, the Welsh Government announced publication of its supplement to the UK plan for tackling roadside nitrogen dioxide concentrations in Wales.  This sets out an action plan of measures to be taken at the five exceedance locations on the trunk road network (Table 10, page 56), as well as a table of Precautionary Retained Measures (PRM) (table 11, page 57).

For Junction 41-42, the action plan measure identified is a “50 mph Speed Limit from the end of the current 50mph speed limit near Junction 41 (Baglan) to Junction 42 (approximately 5.0km)”. However, the “closure of junction 41 westbound on-slip, plus 50mph speed limit” (option B above) is retained as one of two PRMs.

Welsh Government Response

The letter to the Chair from the then Cabinet Secretary for Economy and Transport confirms the position described above.   He indicates that:

NO2 concentrations at each of the 5 locations are currently being monitored by diffusion tubes and the intention is to supplement these with continuous monitoring using reference method analysers by the New Year. As part of the monitoring exercise, the effect of speed limits on air quality is being reviewed and the results fed into the investigations and modelling to establish if further measures are required to achieve compliance in the shortest possible time. This is where the precautionary measures may be required.

I recognise the strong local desire to keep open Junction 41 of the M4. However the Welsh Ministers have to consider all measures that could reduce exposure to NO2 as quickly as possible and to present options as part of the consultation process in order to comply with the Ambient Air Quality Directive (2008/50/EC) and the Air Quality Standards (Wales) Regulations 2010. The consultation on the WelTAG Stage 3 appraisals was the most recent stage in the process and that consultation sought views on the proposed measures to reduce exposure to NO2 at five locations in Wales, one of which is Port Talbot.    While we have considered the measures against set criteria and objectives, we must take into consideration that exposure to heightened air pollution does pose a threat to life, and consider not just road users, but also the people who live and work near the motorway and trunk road network and the wider public. Therefore, the future closure of Junction 41 cannot be ruled out at this stage.

Should we establish that development of the relevant ‘Precautionary Measure’ or any other measures to reduce NO2 levels on this section of M4 are necessary, engagement with all stakeholders will then be undertaken.

National Assembly for Wales Action

The trial closure of junction 41 was discussed extensively during the Fourth and Fifth Assemblies.  A range of issues were raised by Members from across the political spectrum. These focused on the impact of closure on local traffic, emissions on local roads and the wider impact on communities and local businesses in the area.





[1] The “hard measures” were in contrast to “soft measures” which are described as “those that passively reduce NO2 levels by increasing peoples’ awareness to the problem and encouraging a behaviour change.” These were described as having “marginal indirect benefits” which “could provide benefits at all five locations on the network, and potentially across the Welsh [Strategic Road Network].”