Data held on the Bus Emissions Abatement Retrofit programme: EIR release

Information request and response under the Environmental Information (Scotland) Regulations 2004

Information requested

Copies of all data held by Transport Scotland on the performance of buses retrofitted under the Bus Emissions Abatement Retrofit programme, covering the period January 2019 to April 2021. Specifically, for each retrofitted vehicle please ensure the information provided clearly details the maximum exhaust temperatures; the NOx reductions emissions achieved; and where in the country the vehicle operates/operated.


As the information you have requested is ‘environmental information’ for the purposes of the Environmental Information (Scotland) Regulations 2004 (EIRs), we are required to deal with your request under those Regulations. We are applying the exemption at section 39(2) of the Freedom of Information (Scotland) Act 2002 (FOISA), so that we do not also have to deal with your request under FOISA.

This exemption is subject to the ‘public interest test’. Therefore, taking account of all the circumstances of this case, we have considered if the public interest in disclosing the information outweighs the public interest in applying the exemption. We have found that, on balance, the public interest lies in favour of upholding the exemption, because there is no public interest in dealing with the same request under two different regimes. This is essentially a technical point and has no material effect on the outcome of your request.

Please find attached a copy of all data held relating to performance of buses retrofitted under the Bus Emissions Abatement Retrofit (BEAR) programme, covering the period January 2019 to April 2021. Please note that we do not hold maximum exhaust temperature details; however we do hold other exhaust temperature records and these have been provided.

We have also provided the following background information on the BEAR scheme for context. The BEAR grant programme was initiated to support the early adoption of LEZ emission standards for the bus and coach sector in Scotland by providing funding assistance for the retrofitting of mid-life vehicles operating within Scottish AQMAs and LEZs (to Euro VI standard).

BEAR grant awards are only made available for equipment which has been approved by the Energy Saving Trust through the Clean Vehicle Retrofit Accreditation Scheme (CVRAS). Retrofit manufacturers must evidence that their equipment has undergone laboratory testing to achieve CVRAS accreditation for each make/model of vehicle.

Once in-service the performance of the systems has been further evaluated by us, in association with the Energy Saving Trust, through a comprehensive programme of emissions monitoring. The monitoring has provided data from three sources:

  • Telematics data on NOx reduction performance exported from the retrofitted equipment
  • Portable Emission Measurement System (PEMS) testing by independent specialist contractors of NOx and particulate emissions
  • Remote sensing emissions monitoring

One of the principal goals of the BEAR programme is particulate reduction, with evidence from inservice testing of BEAR retrofits showing particulate reduction of up to 99.9% being achieved. In addition, the systems are designed for the abatement of NOx gases, with a daily NOx reduction target of >80%, although up to 97% is being achieved in some cases.

We identified through our monitoring programme that some of the retrofitted buses have not been delivering expected levels of NOx reductions in-service, and we have therefore been liaising with operators on measures to improve the NOx reduction performance. Various interventions have been identified (e.g. enhanced maintenance, fitment of heat shields, adjustments to dosing strategies, and placement of thermocouples) which are showing positive signs of improvement.

In summary, the BEAR programme to date has successfully delivered in respect of reductions in particulates and NOx emissions on the whole. Grant funding is only being provided to operators where the evidence demonstrates that fitted equipment is meeting industry in-service standards, and we will continue to engage with operators to ensure the programme continues to reduce emissions of NOx and particulates in order to benefit human health.

Due to the size of the files we are unable to upload the documents referred to above. If you wish to consider, please contact us at the address below and we will be happy to provide.

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Central Enquiry Unit
Phone: 0300 244 4000

The Scottish Government
St Andrews House
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