World-Harmonized Light-Duty Vehicles Test Procedure

Published: 2013.11.22

Peter Mock

On November 14, the formal text for the World-Harmonized Light-Duty Vehicles Test Procedure (WLTP) was adopted by the United Nations Working Party on Pollution and Energy (GRPE). That decision must still be confirmed by the World Forum for Harmonization of Vehicles Regulations (WP.29) at its March 2014 session. If the WP.29 does confirm the GRPE decision, the WLTP will be complete and ready to be implemented by individual countries.

Regulations governing light-duty vehicle emissions and fuel consumption vary significantly across countries and markets. Manufacturers face additional costs to certify their vehicles under several procedures and standards, even though the fundamental purpose of all regulations is essentially the same: to reduce pollutant emissions and improve fuel efficiency. Harmonizing the test methodology and the test cycle will reduce these costs to the benefit of both manufacturers and consumers. A harmonized approach will also make it easier to compare fuel efficiency and emission standards across regions and countries. Over time, this will improve the effectiveness of air quality targets and CO2 reduction policies.

The development of the WLTP comprised two main elements:

  • Development of a harmonized driving cycle representative of world average driving conditions (internally referred to as the DHC)
  • Development of a harmonized test procedure that sets the conditions, requirements, tolerances, etc. for the emissions test (internally referred to as the DTP)

Since the beginning of the WLTP process, the European Union has had a strong political objective, set by its own legislation (Regulations (EC) 443/2009 and 510/2011), to develop and adopt a more realistic test procedure by 2014. This was a major driving factor for setting the time frame of phase 1 of the WLTP. Similarly, Japan has also agreed to adopt the WLTP for its fuel efficiency standards, and the existing Japanese 2020 efficiency target for new vehicles will likely be adjusted for the WLTP.