Solving the Clean Air Zone Conundrum 

For a number of local authorities, the UK plan for tackling roadside NO2 concentrations presents a significant challenge, requiring them to improve poor air quality as quickly as possible.

Whilst the latest ultra-clean Euro VI buses and advanced electrified options comfortably meet clean emission requirements, a significant majority of the older, existing bus fleet are seen as being a significant source of pollution and need a rapid and cost-effective solution.

Launching today is the Clean Vehicle Retrofit Accreditation Scheme (CVRAS) developed jointly by the Low Carbon Vehicle Partnership (LowCVP) and the Energy Saving Trust (EST) together with industry stakeholders through funding and support from the DEFRA/DfT Joint Air Quality Unit (JAQU). By providing a single standard for any emission technology to be validated to meet the standards set out in the government’s Clean Air Zone Framework for England, the scheme will enable the existing fleet of urban vehicles (initially buses, but extending rapidly to a wide range of vehicles) to be fitted with proven emission control solutions. The scheme will provide the backbone of future retrofit funding, enabling the UK market to lead this important sector.

Larger vehicles (buses, vans and HGVs) contribute over half of UK national average roadside concentration of nitrogen dioxide according to Defra’s AQ analysis. In 2018 the UK Government will publish a comprehensive Clean Air Strategy which will address other sources of air pollution.

The Clean Vehicle Retrofit Accreditation Scheme will provide independent evidence that a vehicle retrofit technology will deliver the expected emissions reductions and air quality benefits in real world operation. It will enable drivers, technology manufacturers, businesses and local authorities to be confident that properly verified and accredited technologies provide the appropriate emissions reductions to meet the standards in the government’s Clean Air Zone Framework for England.

The initial objectives of the scheme, are to develop a set of test protocols (using the existing bus and commercial vehicle technology evaluation schemes as starting points) to accredit retrofit technologies which will deliver on road emission levels equivalent to. Euro VI/6, based on the best available data and representative operating cycles.

The retrofit accreditation process will be technology-neutral and designed to allow all potential suppliers of eligible, credible emission reduction technology to apply for accreditation.

Technologies already potentially identified and in common use include: SCR (Selective Catalytic Reduction) fitted to exhaust systems, hybrid powertrain systems and engine repowers with gas (LPG or CNG). New technologies will need to provide robust, independent relevant test data of the performance, prior to being considered for CVRAS accreditation.

LowCVP’s Managing Director, Andy Eastlake said: “The most effective retrofit technologies can cut polluting emissions by over 95%. But it is critical that these systems are properly calibrated and matched to the vehicle and its operation and that we have a common and robust approval system.

“By making sure that we fit a range of the most appropriate technologies to the right vehicles, retrofitting can make a very significant, immediate impact on our air quality problems, supporting the complementary strategy to adopt new vehicles as quickly as economically viable.

“As you would expect from the LowCVP, our accreditation process will also ensure that there is no adverse impact on fuel efficiency or carbon emissions and aims to maximise the simultaneous benefits for both the environment and climate”

EST’s Transport Certification Manager, Colin Smith said: “Air pollution in our towns and cities is a major issue and one that everyone wants to address. Road transport is the big contributor and it will take some time before the newer cleaner vehicles replace the current fleets out there.

“By appropriately retrofitting the legacy fleet will bring immediate benefits. However, having confidence in which systems to fit and which solutions work is key for both vehicle operators and the local authorities implementing CAZs”.

“This is where a robust certification scheme will play a vital role and give assurance to stakeholders in verifying the emission reduction technologies and those that supply them in a consistent, comparable and trusted manner. As the scheme has been set up as technology neutral, any new technology can also be tested in a consistent a comparable way ensuring that real emissions reductions are achieved and air quality is improved for all.”

Any potential suppliers interested in finding more about the CVRAS should visit the EST website or email