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UN adopts a more robust method to detect particle emissions from diesel vehicles

rear view of cars in traffic

UNECE’s World Forum for Harmonization of Vehicle Regulations (WP.29) has adopted an amendment to the United Nations Rule No.1 of the 1997 Agreement that allows for the introduction of a more robust test procedure to measure exhaust particle emissions during periodic technical inspection tests for all diesel light-duty vehicles (passenger cars and vans) equipped with diesel particulate filters.   

The new amendment is the latest in a series of regulatory decisions adopted by the World Forum aimed at ensuring global harmonization of periodic technical inspection tests to guarantee that all vehicles deployed on the road are safe and clean.  

The new procedure is performed using a particle counting instrument (PN-PTI), which provides a more accurate assessment of exhaust emissions and can thus better identify high emitting vehicles that are responsible for the majority of air pollution from traffic in urban areas.   

The PN-PTI test offers a reliable and quick way to detect high emitters and can help detect particulate filter removal and tampering, or other malfunctions. It is performed at idle, with the vehicle stationary, using a portable PN tester.  

The PN-PTI test replaces older methods based on smoke measurement (smoke opacity tests) that are not sensitive enough for modern diesel engines. The test is applicable to diesel vehicles with filters meeting the Euro 5 and 6 emission standards, and has recently been deployed in Belgium, Germany, the Netherlands and Switzerland, where it has proven its cost effectiveness and efficiency in detecting high emitters. 

Following the entry into force of the amendment to UN Rule No.1 on 21 June 2024, all contracting parties to the 1997 Agreement now have the option to deploy the PN-PTI test, which has the potential to reducing the harmful impact of vehicle exhaust on air quality, health and the environment.   

Note to editors   

About the World Forum for Harmonization of Vehicle Regulations  

The World Forum for Harmonization of Vehicle Regulations, hosted by UNECE, is a unique global platform responsible for the regulatory frameworks regarding the safety and environmental performance of vehicles, their subsystems and parts.   

The World Forum manages three Global Agreements on vehicles: 1958 Agreement (UN Regulations); 1998 Agreement (UN Global Technical Regulations); and 1997 Agreement (UN Rules on Periodic Technical Inspections). Any country that is member of the United Nations may participate in the activities of the World Forum and accede to the Agreements.  

The Working Party on Pollution and Energy (GRPE) is one of the six subsidiary bodies of the World Forum. It concentrates its work on defining exhaust, energy efficiency and power measurement procedures for all modes of inland transport in order to limit environmental damage.  

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