Transport Emissions and Air Quality

We assists local authorities, central government, planners, developers and others to measure, model, understand and improve air quality and minimise emissions.


We have over 40 years’ experience in this field and provide a wide range of services including air quality and emissions modelling, monitoring, emissions inventories, development of driving cycles, roadside vehicle emissions testing, air quality action plans and bespoke solutions for sustainable and low emission transport.

Local authority air quality management LAQM

  • Review and assessment reporting (ASR and APR)
  • Technical and policy guidance
  • Links with public health and climate change
  • Stakeholder engagement
  • Continuous and passive AQ monitoring systems

Actions to improve air quality

  • Low emission solutions including CAZs and LEZs
  • Air quality action plan development
  • Scenario modelling
  • ANPR surveys, vehicle counts and classification
  • Source apportionment

Vehicle emissions

  • Roadside vehicle emission testing and remote sensing
  • Alternative fuels and power trains
  • Transport emission factors
  • Emission modelling and inventories
  • Novel and bespoke emission modelling tools

Driving characteristics

  • Vehicle instrumentation and drive cycle development
  • Development of real world test cycles
  • Evaluation of driving styles e.g. eco-driving
  • Impact of traffic management scenarios on driving characteristics

Planning support

  • Planning application review
  • Major scheme air quality assessments
  • Development of guidance
  • Construction and demolition fence-line monitoring

Project examples

  • Developing instantaneous emission models
  • Real world emissions Vs type approval
  • Low speed stop-start emissions
  • Emission tools for road, rail, air & shipping
  • LEZ and LES feasibility studies for UK cities
  • Geographic specific emission inventories
  • Emission and air quality impact assessment of managed motorways and UTMC
  • State of the art remote sensing device
  • Emission based car parking
  • ULEV technology and charging infrastructure

Local authority reporting

Under the Local Air Quality Management (LAQM) legislation all local authorities in the UK have an obligation to review Air Quality and assess levels against the national objectives. Where concentrations exceed the set levels an Air Quality Actions Plan (AQAP) is required to address the issue. This area of work now also covers the Clean Air Zones recently introduced around the country on polluted traffic routes.

Our Air Quality monitoring team offer a range of bespoke services associated with the initial identification of problem areas and continued real-time measurement of NO2, SO2 CO2, O3, Particulate matter, airborne metals, PCB’s and PAH’s.

Our team have completed over 150 projects ranging from a 6 month diffusion tube survey through to 10+ real-time instruments measuring at 4 locations for a 3 year period campaign, including:

  • Initial investigation campaigns with passive devices such are diffusion tubes, sticky pads and indicative dust monitors.  
  • Monitoring support services of existing Local authority monitoring site through our dedicated internal engineers, this can include routine calibration visits, servicing, maintenance, data collection and site re-location.
  • Complete site operation using bespoke monitoring packages to cover the whole monitoring campaign, this can include, site selection, equipment supply, calibrations, maintenance, data collection and reporting.

Construction consultancy

Many large scale construction projects require environmental impact assessments, as part of these documents the impact on air quality through construction must be considered. These considerations are not limited to construction dust alone and regularly include the potential for increased pollution due to changes in traffic flows, increased emissions from industrial processes / Energy from Waste (EfW) sites. In the greater London area where all Boroughs are covered by Air Quality Action Plans (AQMS), all construction sites over a given size require real time continues dust monitoring of PM10 as a minimum. For dust monitoring at construction sites TRL hold a stock of indicative dust monitors, which are easy to install and provide a good level of data capture, these instruments offer automatic reporting and alerts to trigger levels.

For some industrial processes and/or sites a pre-planning assessment of air quality level may be required, this is used to determine the current levels and determine the impact of the construction on the wider area. This may then be extended through the construction phase and into post completion to assess the true impact. This type of assessment will normally include PM10/2.5 and NO2 concentration but may also include airborne PCB’s, PAH’s and Metals levels.  

Emergency response monitoring

Working closely with the environment agency and Public Health England, we have developed a robust capability for monitoring the impact of large commercial fires on the surrounding air quality. During the initial stages of a large fire the Environment Agencies response team will attend to monitor the pollution levels for the first 48-72hrs, after this period monitoring is left for the local authority involved to arrange. Our Air Quality team have attended several large commercial incidences where it has not been suitable to completely extinguish the fire, this may be due to the environmental impact of contaminated water run off or other surrounding issues. Some of these fires have smouldered for several months and to assess the impact to local residence and the wider environment a range of pollutants have been measured. Each site is different but, monitoring has ranged from passive TENNEX tubes through to 10+ instruments measuring a range of air bourn particulate and gases. The data reports from these monitoring campaigns can be tailored to the clients’ requirements covering various aspects for the monitoring and comparisons to W.H.O. limits.          

Following the fire at Grenfell Tower TRL were able to assist Public Health England with the short to medium term monitoring of the potential harmful air borne particulates given off in the aftermath of the incident.

There is only one limited opportunity to obtain these measurements, our stock of equipment, experience and versatility has allowed our team to start monitoring within 24hrs and achieve very high data capture. 

Air quality research

Working closely with our internal environmental consultants and other third parties, our Air Quality Monitoring team have carried out a range of research projects.  These include:

  • An investigation into the effectiveness of a green wall project in Kensington, carried out through the simultaneous measurement of NO2 and particulate matter on either side of the screen.
  • A research project investigating the absorption of NO2 by mycelium (Mushrooms roots).
  • Monitoring Nitrogen Dioxide levels at several London fire stations. This project looked at the potential health impacts to the fire officers from the idling fire engines.     

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