In the late 2000s, the European Commission identified that, although the EU type approval emissions requirements for light duty vehicles had been gradually and significantly tightened over time, these reductions had not been fully translated into equivalent reductions in the actual emissions of these vehicles in real world driving conditions. Therefore, in 2011, the European Commission established a Working Group to develop a Real Driving Emissions (RDE) test procedure to better reflect vehicle emissions in real world driving conditions.
Due to the size and complexity of the equipment required to accurately measure vehicle emissions, all EU type approval emissions testing up until that point in time had been carried out in specific emissions test laboratories on a chassis dynamometer. However, with advances in technology, much more compact emissions measuring equipment had been developed, to the point where the emissions measuring equipment could be made small enough to be mounted directly onto the vehicle under test, thereby allowing the test vehicle to be driven on the road, under real world conditions, whilst its gaseous and particulate emissions are being accurately measured. This type of emissions measuring equipment is referred to as a Portable Emissions Measurement System (PEMS).
The RDE test procedures, using PEMS equipment, developed by the European Commission's RDE Working Group were first introduced into the EU light duty vehicle emissions Regulation in 2016 and, since then, have been further refined, revised and expanded, based on experience gained with their application. Following on from the EU’s introduction of specific RDE requirements into their light duty vehicle emissions Regulation, a number of other countries, including Japan, China and South Korea, have also adopted similar RDE requirements into their national light duty vehicle emissions Regulations.
To encourage the worldwide harmonisation of RDE requirements for light duty vehicles, in 2018, the United Nations Economic Commission for Europe (UN ECE) World Forum for the Harmonization of Vehicle Regulations (WP.29) set up a specific Informal Working Group to develop a Regulation specifying a worldwide harmonised method to determine the gaseous and particulate emissions from light duty vehicles during real world driving conditions. Initially, the intention was to develop a Global Technical Regulation (GTR) on RDE. However, at the request of Contracting Parties, it was agreed to also develop a UN ECE Regulation on RDE in parallel. Between 2018 and 2021, this Informal Working Group met on 13 occasions to develop the necessary Regulatory texts, taking into account the very latest developments in RDE testing from around the world.
The final draft version of the new UN ECE Regulation on RDE testing was adopted by WP.29 at their 190th session in June 2023, officially published on March 19, 2024 and has a date of entry into force of March 26, 2024. This new Regulation has been allocated Regulation No. 168.
The requirements specified within UN ECE Regulation No. 168 include:
- Criteria on the selection of vehicles for PEMS testing, including criteria on the minimum number of tests/vehicles required to validate a PEMS Test Family.
- Detailed technical specifications and calibration procedures for the PEMS equipment.
- Criteria on the parameters which must be met for a valid "RDE trip", including parameters on ambient temperature, altitude, driving dynamics (i.e. accelerations and decelerations), head winds and road grades.
- Requirements on the test vehicle specification and condition.
- Requirements on the proportion of urban, rural, expressway and motorway driving to be included in a valid "RDE trip", and on the average speeds to be recorded during each of these phases of the "RDE trip".
- Detailed procedures and calculation methodologies for assessing the validity of an "RDE trip".
- Detailed calculation methods to establish the final RDE emission results from valid RDE testing.