New roadworthiness rules must require effective, independent and periodic tailpipe testing

DISCLAIMER: All opinions in this column reflect the views of the author(s), not of EURACTIV Media network.

This article is part of our special report Air Quality.

A trilogue this Monday (9 December) will consider new roadworthiness regulations. It is imperative that a proposal to start testing lorries using their on-board controls, rather than testing vehicles at their tailpipes, must be rejected, argues Simon Birkett.

Simon Birkett is the founder and director of Clean Air London, an NGO

Final Trilogue discussions on roadworthiness regulations next Monday must reject the proposal to use on-board diagnostic (OBD) testing as an alternative to tailpipe testing. 

Only an effective, independent and periodic tailpipe test can ensure compliance with emissions standards. International tests have shown that OBD is not a reliable and accurate test method, especially for diesel emissions, as high percentages of vehicles tested did not display any OBD failure, even though they had failed the stricter tailpipe test. At a minimum OBD testing must always be combined with an emission tester.  

An announcement this week by the UK’s Department for Transport (DfT) highlighted the scale of the problems faced by the motor industry when it admitted that some firms are offering services to remove the factory-fitted diesel particulate filter (DPF), claiming it will improve fuel economy, when it is an offence to drive a vehicle that has been modified this way.

An investigation by Clean Air in London (CAL) earlier in 2013 showed that tens of thousands or hundreds of thousands of motorists in the UK may be driving diesel vehicles illegally, face losing their car insurance and risk being found guilty of the criminal offence of fraud – many without realising it. Honest motorists purchasing a second-hand diesel vehicle are particularly at risk. 

The DfT’s announcement is a timely reminder of the importance of fully operational DPFs and emissions control systems and the need for the final Trilogue meeting next Monday to ensure the new regulation of the European Parliament and of the Council on periodic roadworthiness tests for motor vehicles and their trailers includes the effective, independent and periodic tailpipe testing of oxides of nitrogen (petrol and diesel vehicles) and particulates (diesel vehicles only).

OBD alone is not an acceptable option for roadworthiness testing inter alia because it is not a robust, accurate or reliable test method for ensuring compliance with emissions standards. The proposed regime is ambiguous and would result in a patchwork of test methods across Europe.  Economies of scale in testing methodologies would not be achieved. Each vehicle manufacturer would have its own monitoring strategy and no ‘in-service’ checks would be made of a vehicle manufacturer’s OBD software. This would be setting the ‘fox to guard the henhouse’.

Many studies have showed that OBD systems (even for modern Euro diesel and petrol cars) do not function correctly or are unable to detect the removal or manipulation of DPFs or electronic manipulations. In addition, some vehicles cannot communicate with an OBD system and thus require tailpipe testing.

It is essential therefore that the Trilogue requires effective, independent and periodic tailpipe testing to ensure in-use compliance with the environmental standards. Tailpipe testing must remain the default method for diesel vehicles and OBD must only be used as part of a combined test method.

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