Petition Number: P-06-1568   Petition title: Return all the M4 to the 70mph speed limit, in Wales. Remove all lower speed limits forced on us.   Text of petition: The OVERWHELMING MAJORITY believe the Port Talbot 50mph is not required. This is likewise with the 50mph brought in around Newport. It is stiffling our ability to travel freely and causing unnecessary 'snarl ups'. The Government is here to serve the people and better their lives. This is a reduced speed limit, that is neither wanted or required. Modern cars are able to travel very safely with far superior braking distances to older cars when 70mph was the standard motorway speed limit.     The text provided above is submitted by the petitioner. The petitions team make every effort to ensure it preserves their authentic voice. This text has not been verified for accuracy, or errors, and may contain unverified opinions or assertions.

 

1.        Background

Cars with petrol and diesel combustion engines produce a variety of polluting gases, including nitrogen dioxide (NO₂). Production of NO₂ increases with vehicle speed. Lower speed limits can therefore reduce NO₂ concentrations in the air.

Human exposure to NO₂ has negative health impacts. The Welsh Government has a legal duty to comply with air quality regulations, including limits on NO₂ at the roadside. Legal limits are set at:

§    an hourly limit value of an average of 200 micrograms per cubic metre (μg/m³) (which must not be exceeded more than 18 times in a calendar year); and

§    an annual limit value of an average of 40 μg/m³.

Assessment and monitoring previously identified NO₂ levels above the legal limit at several locations on the motorway and trunk road network, including the M4 between junctions 41 and 42 at Port Talbot, and junction 25 to 26 at Newport. In 2018, both the Welsh Government and UK Government were successfully taken to Court over NO₂ levels which exceeded legal limits.

NO₂ concentrations at identified locations on the motorway and trunk road network have reduced since the introduction of 50 mph speed limits in 2018.

2.     Welsh Government action

The Welsh Government consulted on an approach to tackling roadside NO₂ concentrations in the Spring of 2018. In November 2018 it published its ‘Tackling roadside nitrogen dioxide concentrations in Wales’ plan. In terms of the trunk road and motorway network, which the Welsh Government is directly responsible for, the plan noted:

Exceedances of legal limits for NO₂ have been identified on the following discrete stretches of motorway and trunk road outside the Cardiff and Swansea Urban Areas:

(i) A494 at Deeside (North Wales Zone);

(ii) A483 near Wrexham (North Wales Zone);

(iii) M4 between Junctions 41 and 42 at Port Talbot (Swansea and South Wales Zone);

(iv) M4 between Junctions 25 and 26 at Newport (South Wales Zone); and

(v) A470 between Upper Boat and Pontypridd (South Wales Zone).

The plan made clear that NO₂ concentrations were above the 40 μg/m³ limit at these sites. The Welsh Government determined the introduction of 50 mph speed limits as the quickest method of achieving compliance.

In June 2018, 50 mph speed limits were introduced at each of the five sites identified in the plan, with the 50 mph limit made permanent the following year. The Welsh Government has monitored the sites since, and published monitoring reports on its website. The most recent data was published in December 2025, and covers 2018 to 2024.

Roadside M4 NO₂ concentrations at Newport and Port Talbot have fallen since the 50 mph speed limit was introduced. Annual mean levels were below the legal threshold for all monitored locations in 2024. The graphic below shows the average annual NO₂ concentration for monitoring sites where data was recorded in every year since 2018. This comprises six sites in Newport, and five sites in Port Talbot.

Average annual roadside NO₂ concentrations on M4 50 mph sections since 2018

Source: Senedd Research analysis of Welsh Government data

Summarising the changes in roadside NO₂ at the five locations where a 50 mph speed limit has been introduced, the Welsh Government report says:

The trend in concentrations is one of general improvement at all monitoring sites from 2018 to 2024. Although concentrations decreased notably at the majority of sites in 2020, and to a lesser extent in 2021 as a result of the reduction in traffic during the global pandemic, concentrations in 2024 have remained lower than in 2018 and 2019, despite a return in traffic levels to near pre-pandemic conditions. Furthermore, the average speed data collected at each site shows that there is compliance at all five sites with the 50 mph speed limit on all days and in both directions at each location in 2024.

The Welsh Government published its Clean Air Plan for Wales in August 2020. It also introduced the Environment (Air Quality and Soundscapes) (Wales) Act 2024, which was passed by the Senedd in November 2023.

The South East Wales Transport Commission, established by the Welsh Government to consider alternatives to the M4 relief road, published its interim report in 2019. This recommended the introduction of average speed control cameras between junctions 24 and 28, replacing the previous variable speed limit approach. In doing so, the Commission said:

Our analysis suggests an average speed control would help improve the regularity of traffic speeds across the problematic stretches of the M4. A fixed speed limit should encourage vehicles to travel at a more consistent speed, making many journeys quicker and more reliable. A single speed limit should also reduce driver confusion and improve safety.

We have considered and modelled a range of speed limits from 40mph to 50mph and 60mph. Our analysis demonstrates 50mph to be the optimal speed in terms of journey time reliability and journey speeds, also taking account other important factors such as air quality, emissions and noise.

In September 2021, the Welsh Government announced enforcement of 50 mph at all five locations would begin from 4 October that year.

3.     Welsh Parliament action

3.1.          Previous petitions

On 13 May 2024, the Petitions Committee considered petitions P-06-1413 ‘Scrap the 50mph limits on the M4 around Newport and Swansea and on the A470 around Pontypridd’ and P-06-1416 ‘Increase the speed limit on the M4 back to 70mph’. The Committee noted that the speed limit reductions could be reviewed in future if technological developments mean engines become less polluting, such as through uptake of electric vehicles. The Committee thanked the petitioners and agreed to close these petitions without taking further action.

In 2021, the Petitions Committee considered a petition calling for the Welsh Government to “Remove the average speed cameras and 50mph speed limit on the M4 between Newport and Cardiff.” The Committee noted the concerns, whilst recognising that the Wales Transport Strategy emphasises environment, air quality and people’s well-being through focusing on sustainable travel and improved public travel infrastructure. It concluded the Welsh Government has no plans to remove the average speed cameras at present, and agreed to thank the petitioner and close the petition.

3.2.        Discussion in Plenary

Traffic congestion on the M4 between Cardiff and Swansea was discussed in Plenary on 8 January 2025. Altaf Hussain MS suggested “the 50 mph limit should now be unnecessary as other factors will dramatically improve air quality in the area”. The Cabinet Secretary for Transport and North Wales, Ken Skates MS, responded:

…the 50 mph speed restriction was introduced as a consequence of legal action that was taken against Welsh Government—legal action that's been taken against Governments elsewhere as well for the same reason—to help to bring down air pollution. We are hopeful that that measure will be successful, and, of course, if levels of pollution can drop along those routes below the legal threshold, then we'd look at removing those speed restrictions.

In November 2022 Natasha Asghar MS said the 50 mph cameras on the M4 in Newport “simply haven’t worked” as “heavy congestion still plagues that stretch of the road every single day”. She asked, referring to cancellation of the M4 relief road scheme:

… is it not true that the imposition of unrealistic speed limits has less to do with cutting pollution and everything to do with forcing motorists off our inadequate roads to cover up your failure to provide Wales with an effective and efficient road network?

The then Deputy Minister for Climate Change, Lee Waters MS, responded:

The provision of 50 mph speed limits, as the Member knows, were, in many cases, court ordered because they were breaching air quality targets, and, far from her saying have proven ineffective, the reverse is true, as she well knows. They have proven effective in bringing down the pollution levels, as well as contributing to smoother flow of traffic.

 

Every effort is made to ensure that the information contained in this briefing is correct at the time of publication. Readers should be aware that these briefings are not necessarily updated or otherwise amended to reflect subsequent changes.