By Simon Shilton, Acustica
In 2016/2017, in the context of the revision of the EU type-approval framework for L-category vehicles, the European Commission mandated a consortium of experts (Emisia, HSDAC, TNO, and Ricardo) to carry out a study investigating the potential for new sound limits for L-category vehicles at Euro 5 step, including a justified proposal with a Cost-Benefit Analysis of new sound limits options.
The Impact Assessment Institute (www.impactassessmentinstitute.org) and Acustica (www.acustica.co.uk) were commissioned by the European Association of Motorcycle Manufacturers (ACEM) (https://www.acem.eu/), to conduct an independent expert review and reassessment of the 2017 cost-benefit analysis (CBA) study published by the European Commission.
In order to support the work of the IAI and Acustica, ACEM also mandated Graz University of Technology (www.fvt.at) to carry out an experimental study on the actual status of noise emitted from eight powered-two wheelers. This study assessed the major noise sources according to their contribution to the overall level of pass-by noise for these vehicles (i.e. intake noise, engine noise, exhaust noise, and overall noise) and was carried out by conducting measurements according to the standardized pass-by noise measurement procedure as regulated by UNECE-R 41.04.
The reassessment followed the logic of the 2017 CBA’s methodology flowcharts, which calculated benefits from the average sound pressure level reductions alongside each road type for the day, evening and night. This is considered a legitimate and rational methodology for assessing the amenity and health benefits, or costs, of changes in noise exposure. Each element of the methodology was then reassessed, identifying potential alternative calculations and their impact on the benefits and costs.
By reviewing the assumptions, data, and calculations, the reassessment generated alternative benefits, costs, and therefore benefit/cost (B/C) ratios for a 2 dB reduction in the noise limits of L-category vehicles and 25% illegal exhausts.
The reassessment study results rely on the veracity of the following assumptions and simplifications, detailed in the text of this report:
- The impact of fractional dB changes in sound pressure levels can be interpolated between the whole number dB increments in the dose-response relationships.
- The UK dose-response relationship is currently the most robust available.
- The reconstructed flow rates generated from various sources are representative.
- The compliance costs provided by the OEMs with the most representative profile can be used to generalise costs for the whole analysis.
The impact of fractional dB changes in sound pressure levels can be interpolated between the whole number dB increments in the dose-response relationships. The UK dose-response relationship is currently the most robust available. The reconstructed flow rates generated from various sources are representative. The compliance costs provided by the OEMs with the most representative profile can be used to generalize costs for the whole analysis.
NSR testing results from TU Graz confirm the challenging technical interventions required to meet a 2 dB limit reduction and qualitatively support the substantial R&D and manufacturing costs underlying the cost estimates. Robust and accurate cost estimates are however difficult to achieve because of the many systems requiring intervention and are different for different L-category vehicle types.
Cost data are insufficient to generate equivalent benefit/cost ratios for a 5 dB limit reduction. NSR results indicate that a 5 dB limit reduction would likely be infeasible for smaller motorcycles and very challenging or potentially infeasible for larger motorcycles.
Results of the reassessment and the experimental noise source ranking are available to download: