Transport Blog

Cut air pollution: De-prime the A346/A338!

Published by Sam Page on 16 March 2016

Image In April 2015, the UK Supreme Court ruled that the Government must take immediate action to cut air pollution levels throughout the country. This means that the Environment Minister, is legally bound to produce plans that will reduce harmful emissions, such as nitrogen dioxide and particulates, down to levels that will not affect the health of vulnerable people, 'in the shortest possible time' before 2020.

Marlborough Area Board Councillors requested that Transition Marlborough host a public meeting in order to come up with an Action Plan that would cut air pollution. The public meeting was held on 10th February and was attended by 35 residents. You can download the full report on this meeting: Improving Air Quality in Marlborough  - or read the summary below:-


  1. Wiltshire Council (WC) designated Marlborough an Air Quality Management Area in 2010. This obliges local authorities to: 1) Monitor air quality (levels of nitrous oxides and ultra-fine particulates) in the town; 2) Prepare regular Action Plans to inform the Highways Agency of the nature and extent of the problem and define the role that the Highways Agency needs to take in relation to air quality improvements; 3) Refuse development within or adjacent to an AQMA unless measures are taken to mitigate air pollution.

  2. Current Nitrogen dioxide levels, as measured along the A346 (Salisbury Road, London Road, Barn Street, Herd Street) appear to be illegal, as they continuously exceed the mean annual legal limit of 40µg/m3. PM10 levels on London Road (opposite St Peter's School) have exceeded 100µg/m3 ten times since the beginning of 2016.

  3. Between 2008 and 2013, several Wiltshire councillors, with constituents living alongside the A346/A338, worked to get the route de-primed in order to encourage through traffic, including HGVs, to use the A34 to travel between the A303 and the M4. Once the route is de-primed weight/width/night-time restrictions or a 'low emissions zone' can be introduced. This could significantly reduce the volume of unnecessary through traffic, including HGVs and associated toxic emissions.

  4. WC appears to have blocked all attempts to de-prime this route. This is because transport planners estimate that only 50% of through traffic, between 7am and 5pm, i.e. 33 HGVs, would transfer to the A34. This does not take into account the impact of vehicle restrictions and the ability of local 'Lorry Watch' teams to police them. Recent correspondence suggests that there continues to be misunderstandings between WC and members of the A338/A346 Working Group regarding this issue: the Senior Transport Planner recently stated that “the Working Group believed that de-priming would not deliver the desired outcomes along the corridor”, while the view of the Working Group “remains that de-priming would be helpful in reducing some of the noise and emissions pollution, but it became clear that Wiltshire Council had and still has no intention to take this forward due to the lack of funding and the likely low cost-effectiveness of de-priming.”

  5. While the cost of de-priming is high (at least £250,000) it is much less than the cost of constructing a by-pass. De-priming would also reduce emissions and provide relief to several thousand families living alongside the A346/A338.

  6. WC has recently given the go-ahead for a new housing development on the Salisbury Road. The statutory measures for the mitigation of air pollution suggested by the developer and accepted by WC, will neither improve air quality, nor address increased pollution from the expected 200 extra cars. Part or all of the cost of de-priming the A346/A338 could be requested from the developer.

  7. It is therefore in the public interest that the following questions are addressed by WC:

  • What evidence is there that WC has worked with the Highways Agency to improve air quality in Marlborough, in accordance with DEFRA's regulations?​

  • The Wiltshire and Swindon Freight Quality Partnership, which is responsible for planning HGV routes, claims 'to encourage freight best practice and to develop the environmentally sensitive, economic and efficient delivery of goods throughout Wiltshire'. Why is 'improving air quality' not mentioned in the Terms of Reference for this partnership?
  • Now that WC has the responsibility for re-classifying roads in the county, why hasn't it taken forward the plan to de-prime the A346/A338, including removing Marlborough from the list of primary destinations?
  • Considering the responsibility on the developer of the new Salisbury Road housing estate to mitigate air pollution, why wasn't this company asked to cover the costs of de-priming the A346/A338?
  • Considering that levels of Nitrogen dioxide appear to be illegally high along the stretch of the A346, between 13 Salisbury Road and 27 Herd Street, with many residents, including children at St Peter's School (situated alongside the A346) suffering from asthma or other respiratory diseases, how can WC fulfil its legal responsibility to improve air-quality in Marlborough by 2020, without de-priming the A346/A338?
  1. Traffic is likely to increase on the A346 and the A4 as a result of cuts to subsidised bus services.

  2. Other remedial measures such as improving the cycling infrastructure and obliging bus drivers to switch off idling engines, while waiting at bus stops were popular with residents.

  3. Transition Marlborough has undertaken this research and completed this report, to assist the Area Board in fulfilling its obligation to prepare an Action Plan which will reduce air pollution to safe levels by 2020. We hope that the evidence contained in this report will enable the Marlborough Area Board Councillors to work with other Councillors representing constituents along the A346/A338 corridor, WC's Public Health and Sustainable Transport Teams and Highways England, to de-prime this route. We believe that this is the only action that can reduce air pollution significantly, within the terms of the Supreme Court ruling.