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Clean vehicle retrofit accreditation scheme

CVRAS retrofit maintenance guide

To make sure buses fitted with Clean Vehicle Retrofit Accreditation Scheme (CVRAS) retrofits are working correctly, their systems need to be monitored and maintained. 

If you’re a driver or fleet manager, you can use the in-cab displays and telematics to monitor system performance and identify any issues or possible faults. 

Continuing to operate a bus with a faulty or disabled system can lead to higher repair costs, so it’s important to fix these early on. A failed system also emits pollutants that are harmful to health. 

Here’s our advice for maintaining retrofit emission reduction systems. 

How do I become Clean Air Zone compliant with CVRAS approved retrofit systems?

Clean Air Zones improve air quality in traffic hotspots by encouraging the replacement of old, polluting vehicles with lower emission vehicles. Cleaner vehicles can enter these zones for free, while older vehicles must pay a charge (or are issued a penalty for non-payment).

The emissions standard for diesel buses to comply with Clean Air Zones is Euro VI. Retrofit technology has been designed to treat the exhaust emissions of older vehicles, reducing harmful emissions and making the vehicle compliant with the Euro VI emissions standard. Only retrofit systems accredited under the CVRAS are allowed to enter the zones.

To help the bus industry meet the emission requirements, funding was provided to fit CVRAS retrofit systems to over 9,000 buses across the UK. To make sure they continue to operate effectively and retain their low emission status, the systems and buses must be monitored and maintained.

CVRAS details the systems, suppliers and requirements needed to be compliant. Vehicles with approved retrofit systems are logged on the GOV.UK vehicle checker for driving in a clean air zone.

Retrofit technology

Suppliers have developed retrofit solutions that can lower the NOx and particulate emissions of older vehicles to levels similar to Euro VI. Retrofit systems approved through CVRAS are exempt from emission zone restrictions in the UK.

There are four main suppliers of CVRAS approved systems to UK bus market:

Systems are monitored through a telematics monitoring unit and web portal and the core retrofit vehicle technology:

Case studies

Last updated: 28 October 2024