Air quality

Transport Scotland aims to deliver environmental protection and minimise environmental impacts by measuring, monitoring and managing transport impacts on air quality, whilst complying with statutory air quality limits.

Transport Scotland is undertaking the following activities on air quality:

• Supporting the delivery of the Cleaner Air for Scotland strategy (CAFS)
• Supporting the Local Air Quality Management process
• Collaborating with partners including Scottish Government, SEPA and local authorities to protect and improve air quality via the CAFS governance group, the Scottish Transport Emissions Partnership (STEP) and E-cosse
• Understanding air pollution along our transport networks
• Undertaking research into low cost monitoring of roadside air quality via the Collaborative Sensor Research Programme
• Engaging with the Highways England, Department for Transport, Defra and the World Road Association on air quality assessment methods and research

Cleaner Air for Scotland (CAFS) is Scotland’s first national air quality strategy and sets a vision for Scotland’s air quality to be the best in Europe. CAFS draws together Scottish Government policies which impact upon air quality into a single framework and sets out a series of actions for delivering further improvements to air quality. The approach also highlights the opportunities to generate efficiencies and cost savings by linking air quality to other areas, such as climate change adaption and mitigation, transport and planning.

CAFS contains actions across six objectives: transport, health, placemaking, climate change, communications and legislation/policy; the goal being to protect human health, natural environments, and reduce health inequalities.

There are a number of important new initiatives in CAFS:

• A National Modelling Framework, which will provide a standard air quality assessment methodology for use across Scotland at the regional and local scale
• A National Low Emission Framework, which sets out a procedure for local authorities and our Agencies to determine effective measures that will address air quality issues at the local level
• Adoption of the World Health Organisation guideline values for particulate matter into Scottish legislation – making Scotland the first country in Europe to do so
• Developing a national air quality awareness campaign, to inform key audiences and encourage behavioural change

CAFS has been produced in partnership with a number of organisations across both the public, private and third sectors. Successfully addressing air pollution will require a partnership approach, involving the Scottish Government, its agencies, local authorities, business and industry, professional institutions, non-governmental organisations, and the general public.

In Scotland, the majority of the Air Quality Management Areas are located in on or near national or local roads, where these sites are not meeting EU air quality targets for NOX and PM10. Con­struc­tion activ­i­ties on our net­works can also lead to short-term air qual­ity effects.

Air quality is measured by the type and concentration of pollutants. The pollutants of most concern near roads are nitrogen dioxide (NO2) and particles (PM10) in relation to human health and oxides of nitrogen (NOx) in relation to vegetation and ecosystems.

CAFS outlines a series of transport-related actions to improve air quality:

• Ensuring appropriate public bodies have a corporate travel plan
• Delivering the National Walking Strategy Delivery Plan
• Delivering the shared vision in the Cycling Action Plan for Scotland that by 2020 10% of everyday journeys will be made by bike
• Reviewing support for green buses
• Evaluating how the Bus Investment Fund can support local air quality improvements
• Review the Bus Operators Grant to incentivise the use of low emission buses
• Review guidance on powers available to local authorities regarding bus services and how these might positively contribute to local air quality improvements.
• Continue the implementation of Switched On Scotland
• Working with partners to investigate the use of hydrogen as a transport fuel along with exploring the role of less carbon intensive fuels such as liquid petroleum gas, compressed natural gas and biofuels.
• Encourage local authorities with AQMA’s to create a Freight Quality Partnership and to encourage the FQP’s to extend their activities to consider the environmental impact of freight transport
• Reviewing Ministerial guidance on Regional and Local Transport Strategies, with a focus on air quality management.
• Examining the trunk road impact on AQMA’s and implement mitigation where trunk roads are the primary cause of poor air quality.
• CAFS also outlines measures requiring further investigation including:
  • Investigating and supporting European Real Driving Emissions procedures
  • Investigating the merits of a scrappage scheme for the oldest dirtiest vehicles
  • Understanding how fiscal understanding how Vehicle Excise Duty might be used for transport maintenance activities
  • revisiting the reporting and target setting requirements of the Road Traffic Reduction Act 1997
  • Undertaking research into reviewing the role and contribution of lower speed limits to improving air quality in certain locations
  • examining how (i) resident and trade visitor parking policies and (ii) allowing certain vehicles to use bus lanes could encourage the uptake of low emission vehicle (and motorcycle/scooters)
  • understanding how the principle of ‘last mile’ logistics could be adopted across Scotland with a particular focus on targeting city centres with AQMAs
  • Reviewing ITS solutions across relevant AQMAs to optimise traffic flows and prioritise urban cycle corridors as part of the National Low Emission Framework

Scottish Transport Emissions Partnership (STEP) is a collaborative and cross professional Air Quality Technical Group that provides technical support to Scottish organisations working to address poor air quality caused by emissions from road transport. STEP's mission is to work with stakeholders to improve and protect Scotland's urban air quality, by communicating examples of best practice and promoting well-informed and open debate.

STEP has the following remit:

• provide a forum for transparent dialogue, debate and information exchange
• identify and promulgate examples of good practice
• promote a collaborative approach (both internal and externally) to the development of workable and practical LAQM guidance and advice (where Local Authorities have responsibility for managing the 30 Local Air Quality Management (LAQM) areas across Scotland)
• coordinate technical support for local authorities to tackle poor air quality
• provide feedback, information, advice and input to local authorities with a designated AQMA
• assist local authorities who are creating, reviewing, revising or improving an Air Quality Action Plan
• identify need for appropriate research and/or training where appropriate
• create database of organisations that can offer financial support for projects
• identify, engage with, and make efficient use of other relevant stakeholder groups in delivering agreed actions
• define and deliver specific short, medium and long term actions to deliver the above remit

Research into air quality near the trunk road network was undertaken by Transport Scotland between November 2013 and December 2015 via a collaborative sensor rotation sensor programme. The aim of the CSRP was to gain confidence in the application of lower cost, lower powered, redeployable AQM equipment to provide higher spatial and temporal resolution air quality data, collected in parallel with traffic data. We piloted the instillation of low cost, mobile sensors, namely two TDC Systems HI-TRAC Particulate Monitors (HI-TRAC PM units) and two Geotech AQMesh units at the following trunk road sites in close proximity to Air Quality Management Areas and at a Defra automatic AQM site, to allow direct comparison to reference data:

• A90 Dundee, Kingsway
• A9 Perth, Broxden
• A985, Rosyth
• Townhead, Glasgow

The CSRP worked closely with a range of partners to deliver the following objectives:

• to create a collaborative AQM community, to inform and exchange information on the CSRP, and share developments and application of lower cost AQM
• to measure roadside air quality levels and to link these to traffic flow and fleet characteristics
• to identify the most effective, economical, and low maintenance air quality sensor system
• to define the relevant air quality and traffic related metrics

The CSRP is now complete and detailed briefing notes and a final project report are listed below.

Briefing notes

• CSRP Broxden Rotation Report
• CSRP Dundee Rotation Report
• CSRP Rosyth Rotation Report
• CSRP Townhead Rotation Report
• CSRP Project Summary

Next steps

Full project data from the CSRP is available for research purposes on application. The CSRP equipment is currently deployed, and a more developed low cost sensor system is currently being explored.

Kincardine CSRP deployment – Forth Road Bridge Closure

In early January 2016, Transport Scotland took the opportunity to deploy low cost air quality technologies to monitor the air quality adjacent to the A985 near to the town of Kincardine. This analysis was initiated as part of the Forth Road Bridge closure. The air quality monitoring equipment was installed between 15 and 29 of January and removed on 8 March, providing air quality data during the FRB closure and for two weeks after the reopening.

This report determines whether indicative air quality emissions increased as a result of the change in traffic composition on the A985 diversion route, and concludes that there was no significant increase in levels of NO2 or PM2.5 concentrations at the Longannet Roundabout for the period of the FRB closure.

• Collaborative Sensor Rotation Programme: Kincardine – Forth Road Bridge Closure

Emissions Testing of Two Auxiliary Transport Refrigeration Units

As part of a Ministerial commitment made in the Clean Air for Scotland 2 strategy published July 2021 to explore emissions from Non-Road Mobile Machinery, we commissioned a piece of research to be carried out by their consultant specialist Zemo. This report presents results from measuring emissions of two auxiliary Transport Refrigeration Units (auxTRUs). The tests were carried out in a temperature controlled environment where data such as; fuel consumption (whereby CO2 emissions can be computed), Nitrogen Oxides (NOx), particulate mass, particulate number as well as internal and external temperature were measured and analysed.

This report gives Scottish Ministers further understanding of the level of greenhouse gasses emitted by these auxTRUs. Additionally, it aids the overall understanding of how auxiliary diesel engines potentially impact surrounding air quality and helps to overcome the knowledge gap we have in this area.

We are committed to improving air quality. This work was commissioned to help further our understanding of the effects that transport related activities have on our environment. We will continue to engage with the industry to work towards finding suitable mitigation measures.

Read the Transport Refrigeration Units report