Brake wear particle emissions: cost-benefit assessment of scenarios for limits

European Automobile Manufacturers Association -

To further put the Euro 7/VII Regulations into context and to provide new data, ACEA tasked AERIS Europe to examine the impact that possible measures to regulate brake wear particle emissions would have on air quality and in terms of the cost-benefit of certain brake wear reduction scenarios.

The main AERIS Air Quality Report was published in March 2021, summarising the key findings. The second part of the study by AERIS, published in July 2021, is detailed cost-benefit analysis (CBA) of a wide range of Euro 7/VII NOx and PM emission reduction scenarios.

The third part of the study by AERIS, published today, is a detailed CBA of a range of brake particle wear reduction scenarios.

Brake wear particles are a new issue which was briefly addressed during the meetings of the European Commission’s Advisory Group on Vehicle Emission Standards (AGVES) that stopped meetings in April 2021. A lab-based measurement procedure for light-duty vehicle brakes is being finalised in the UNECE informal group PMP (particle measurement procedure).

Data on brake wear using the proposed measurement procedure is being collected in an inter-laboratory test programme (ILS) and ACEA has collected and made available brake wear data which shows a wide variation in measurements which suggests:

  1. More needs to be done to improve the repeatability and reproducibility of the proposed measurement procedure.
  2. Further investigation of the assumed brake wear emission factors indicated by the Commission consultants (CLOVE) in AGVES.

Like for the second part of the study, the methodology behind the CBA is based on the European Commission’s ‘Handbook on the external costs of transport’. It was adopted to ensure alignment with the CBA work which the CLOVE consortium or Commission services are doing on Euro 7/VII.

The Handbook and data from the AERIS Air Quality report enable the calculation of avoided external damage costs to be expressed as the equivalent increase in the cost of a single future new vehicle (ie ‘benefits supported increase’) and adapted using standard discounted cash flow theory.

In other words, if the actual increase in the cost of technical measures would be higher than the benefit supported increase, then the additional benefits would not support the additional cost.

As an example, and using the Handbook figures, the CBA study on brakes indicates that the benefits derived from the introduction of a limit on brake wear particle emissions to achieve a 60% reduction compared to the baseline (from ACEA data) would support an increase in new vehicle cost of €15 to €27 (assumed vehicle lifetime = 10 years) or €18 to €36 (15-year lifetime).

These figures, and many others calculated in the complete CBA study, can be used to compare against data for assumed Euro 7/VII and brake technology costs (plus all other costs such as R&D that would apply to calculate the additional per new vehicle cost for achieving the studied scenarios) in order to test if Euro 7/VII or brake wear scenarios are cost beneficial, or other scenarios or approaches might be more suitable.

While the CBA study considered heavy-duty brake wear, the test methodology for measuring particle wear from heavy-duty vehicle brakes does not exist.