Real-world performance of emissions abatement retrofits to Scottish Buses

Ricardo Energy & Environment is supporting the Scottish government, Transport Scotland and partners, including the Energy Saving Trust, to understand the real-world performance of emissions abatement retrofits to Scottish buses.

The work, known as the Bus Emission Abatement Retrofit (BEAR) programme, utilises advanced remote sensing technology to evaluate the on-road performance of retrofits that are intended to lower bus emissions in support of improving air quality.

Over the past 5 years, levels of air pollution in UK towns and cities has attracted growing public concern and political attention. In 2015, the Scottish Government published the Cleaner Air for Scotland Strategy, setting out ambitious targets to reduce air pollution and laying out an ambitious agenda intended to achieve compliance with European and Scottish Air Quality legal requirements.

A key focus of the Strategy is the reduction of road transport emissions. To enable this, Low Emission Zones (LEZs) have been planned for Glasgow, Edinburgh, Aberdeen and Dundee, as well as being considered as a measure to address other Air Quality Management Areas where appropriate.


The first of Scotland’s LEZs was implemented in Glasgow on the 31 of December 2018. A phased approach was used, focusing initially on reducing NOx emissions from buses operating in a designated area.

Euro VI was set as the required standard for vehicles operating within the Zone, with full implementation required by the end of 2022. The BEAR programme supports this ambition through the installation of Clean Vehicle Retrofit Accreditation Scheme (CVRAS) accredited retrofit technology to buses and coaches in the target cities.

Ricardo Energy & Environment’s vehicle emissions expertise is supporting the programme by evaluating the performance of buses retrofitted through the BEAR programme. Traditionally, such evaluation studies have required the use of on-board Portable Emission Measurement Systems (PEMS).

However, such an approach limits the number of vehicles that can undergo detailed emissions assessment, resulting in a few measurements being assumed to represent the wider fleet. To obtain a more detailed picture of real-world bus fleet performance, Ricardo have deployed advanced remote sensing technology, along bus routes, to provide a more holistic picture of emissions.

Remote sensing

Ricardo’s remote sensing system is used exclusively for the purpose of measuring and quantifying emissions from vehicles. The remote sensing approach has the added benefit of providing information on the wider vehicle fleet including emissions of cars, taxis and LGVs, in addition to buses.

The technology provides a wealth of data that includes repeat measurements of emissions of NOx, NO2, CO, HC, PM and NH3 from target vehicles across a day, as well as the capture of further important parameters such as site conditions, vehicle speed and acceleration.

When this information is coupled with data from automatic number plate recognition (ANPR) cameras — linked to a separate vehicle registry database — it is possible to access even more detailed information on specific vehicle types including Euro Class, vehicle age, mileage etc.

The combination of these two datasets (remote sensing and ANPR) provides previously unavailable insight into vehicle emissions in Scotland’s cities.

To date, remote sensing measurements have been undertaken at locations in Dundee, Glasgow, Renfrewshire and Lanarkshire, in urban and semi-rural locations with the measured emissions from over 30,000 vehicles forming a unique real-world vehicle emissions database for Scotland.

The potential of this database is highly significant as it offers the ability to estimate emissions from all major roads across Scotland, as well as the option of combining datasets with existing ANPR camera infrastructure — adding to the overall level of insight possible.

Such real-world information is invaluable to key decision makers across government. The insight gathered can be used to inform air quality dispersion modelling and allow for tracking of air quality policy to ensure it delivers as intended, cleaning Scotland’s air.

For more information visit Ricardo’s website.


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