Last updated: 20 June 2018

The Welsh Government is introducing temporary 50 mph speed limits and other measures at five key locations to improve air quality for the people of Wales.

The measures are aimed at reducing current high levels of nitrogen dioxide, which exceed legal limits and are damaging to health.

What is involved & which locations are affected? 

The five affected locations are:

Air Quality Locations

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A494 at Deeside

Improvement Measures:

Temporary 50mph speed limit (replacing existing national speed limit) and associated signage to promote smooth traffic flow

Location:

B5125 St David’s Interchange (Holywell Road) to the A458 Deeside Park Interchange (Shotwick Road) at the Welsh/English border (subject to final design)

Approximate Length:

5.9km

Start Date:

Friday 22 June 2018

A494 Deeside

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A483 near Wrexham

Improvement Measures:

Temporary 50mph speed limit (replacing existing national speed limit) and associated signage to promote smooth traffic flow

Location:

J5 (Mold Road Interchange) to J6 (Gresford Interchange) (subject to final design)

Approximate Length:

2.6km

Start Date:

Monday 18 June 2018

A483 Wrexham

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A470 between Upper Boat and Pontypridd

Improvement Measures:

Temporary 50mph speed limit (replacing existing national speed limit), chevron markings and associated signage to promote smooth traffic flow

Location:

Upper Boat Roundabout and the A4058 Roundabout at Pontypridd (subject to final design)

Approximate Length:

4.2km

Start Date:

Wednesday 20 June 2018

A470 Upper Boat-Pontypridd

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M4 between Junctions 41 and 42 Port Talbot

Improvement Measures:

Extension of existing 50mph speed limit west with a temporary 50mph speed limit (replacing existing national speed limit) and associated signage to promote smooth traffic flow

Location:

From end of current 50mph speed limit near J41 (Baglan) to J42 (subject to final design)

Approximate Length:

5.0km

Start Date:

Monday 18 June 2018

M4 Port Talbot

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M4 between Junctions 25 and 26 Newport

Improvement Measures:

Temporary maximum 50mph speed limit overnight (remaining subject to variable speed limits) and associated signage to promote smooth traffic flow

Location:

To the east of J25 (Caerleon Road) to J26 (Malpas) (subject to final design)

Approximate Length:

1.4km

Start Date:

Monday 18 June 2018

M4 Newport

 

Frequently Asked Questions

When can I expect to see these measures introduced?

The initial air quality improvement measures are planned to be in place by the end of June 2018.

Why are you taking action now?

We want to improve air quality for the people of Wales as soon as possible. High levels of nitrogen dioxide are damaging to health and we have a legal duty to comply with the European Ambient Air Quality Directive limit of 40 μg/m3. Current levels exceed the legal limit at the above five locations on the Welsh Government’s motorway and trunk road network and we need to act as soon as possible to maintain public health.

Why speed limits – there must be other measures that would be more effective?

Since we became aware of the five affected locations and level of exceedances, we have been carrying out investigations into all potential measures for reducing nitrogen dioxide in the shortest time possible. Further detailed investigations and modelling are expected to be completed by the end of August 2018. However, from the work already completed to date, we know that 50 mph speed limits have the greatest potential to improve air quality at each location. 

Surely speed limits will just increase congestion? 

Research indicates that nitrogen dioxide emissions are at their lowest when light vehicles, which are the main contributors to nitrogen dioxide at each of the locations, travel at speeds between 40 and 50 mph. As the locations are already affected by high levels of congestion during peak times, 50 mph speed limits are expected to have a smoothing effect, with vehicles travelling at more constant and similar speeds. 

Why are you introducing a temporary 50 mph speed limit overnight between M4 J25 and J26 when most of the traffic is during the day? 

This location is already subject to a mandatory variable speed limit. The optimum speed for the current amount of traffic is automatically calculated to keep vehicles moving at a steady rate. Due to congestion, vehicles on this section of the motorway are already running at lower speeds for long periods of the day. Limiting the maximum speed limit to 50 mph overnight (when there is less congestion and fewer variable speed limits applied) has been identified as the best way to significantly reduce nitrogen dioxide levels in this location. The measure is expected to bring down average nitrogen dioxide levels over a 24-hour period.

How will the temporary 50 mph speed limits be enforced?

Enforcement on the M4 junctions 25 and 26 will be via the existing variable speed limit infrastructure. Enforcement on the other four sections will be approached in the same way as other speed limits on the motorway and trunk road network, in consultation with the police. 

What messages will be displayed on signs associated with the temporary 50 mph speed limits?

Message signs will inform road users of the reason for the temporary speed limits and will encourage drivers to drive responsibly. In combination with lower speeds, these measures have the potential to reduce nitrogen dioxide levels.

How will you know if the measures are successful?

Nitrogen dioxide levels will be monitored at the roadside at each of the five locations to establish the effectiveness of the measures.

How much of a reduction in nitrogen dioxide levels are you expecting?

Based on the investigations and modelling carried out to date, the measures could lead to reductions in nitrogen dioxide levels of up to 18%. However, the actual impact of the measures will be established through roadside monitoring. 

Will the five locations comply with EU Directive limits for nitrogen dioxide after these measures are put in place?

Based on investigations carried out to date, it is possible with these measures alone that the A483 at Wrexham will comply with EU Directive limits this year, the M4 at Newport, M4 at Port Talbot and A470 Upper Boat to Pontypridd in 2021 and the A494 at Deeside in 2022. However, the actual impact will be established by roadside monitoring. 

The full measures needed to achieve compliance at the earliest possible date will be determined by the detailed modelling and investigations due to be completed in August 2018.

Why are the speed limits only temporary?

Temporary speed limits will be in place until roadside air quality monitoring has established their effectiveness and until the detailed investigations are completed in August 2018. The results will determine which measures we need to achieve compliance with the EU Directive at the earliest possible date.

Where can I get more information?

The Welsh Government’s consultation “Tackling Roadside Nitrogen Dioxide Concentrations in Wales” may be accessed via the following link:

https://beta.gov.wales/tackling-roadside-nitrogen-dioxide-concentrations-wales

This FAQs sheet will be updated periodically with the answers to the latest questions received on this initiative.