Clean Vehicle Retrofit Accreditation Scheme

The Clean Vehicle Retrofit Accrediation Scheme (CVRAS)

On behalf of the DEFRA/DfT Joint Air Quality Unit (JAQU), Zemo Partnership (as LowCVP) and the Energy Saving Trust have developed a certification scheme to approve technologies that can be retrofitted to diesel vehicles to reduce NOx and PM emissions and achieve Euro 6 / VI equivalent standards. The Clean Vehicle Retrofit Accreditation Scheme (CVRAS) covers black taxis, vans, trucks, buses and refuse collection vehicles.  Technologies already accredited include exhaust aftertreatment technology, selective catalytic reduction, engine replacement to battery electric powertrain, repower and conversion to LPG and repower with Euro VI engine. The CVRAS scheme has been recognised under the following air quality policies: Clean Air Zones (England and Wales), the Ultra-Low Emission Zone (London) and Low Emission Zones (Scotland).

The scheme is managed by the Energy Saving Trust, with technical support from Zemo Partnership. Full details of CVRAS, accredited technologies and suppliers are available from the CVRAS website.

To support the scheme, LowCVP created a guide that explains the retrofit technologies on the market and their application in different vehicle segments, with supporting vehicle operator case studies, an outline of how they are accredited and the UK air policy framework driving the uptake of retrofit solutions. (Updated by Zemo Partnership in March 2021.)


  • To support the development of new test procedures and accrediting retrofit technologies.
  • To provide technical expertise for JAQU retrofit technology fund for a truck testing programme.
  • To produce and promote a retrofit technology guide.

Project Management and Stakeholder Engagement

This project was managed by LowCVP in collaboration with EST, with input from the Bus, Commercial Vehicle and Passenger Car Working Group members.

Timeline and Deliverables

April 2019 – March 2020

On-going technical support to EST and JAQU.

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