The current laboratory test, known as the Worldwide Harmonised Light Vehicle Test Procedure (WLTP), measures CO2 and pollutant emissions against EU regulations. This standardised testing procedure allows comparison of emissions between different car models.
The Worldwide Harmonised Light Vehicle Test Procedure (WLTP) measures the emissions of passenger cars for both CO2 and pollutants in a laboratory setting. All conditions for vehicle set-up, testing and the handling of test results for cars are defined by EU law. This is important as it establishes a standard regulation that all car manufacturers and other players must respect. Additionally, it allows for a standardised and repeatable procedure which enables customers to compare emissions between different car models.
Laboratory tests not only allow for comparison of emissions between different car models, they also play a key role in the procedure of bringing a car on the EU market. Before vehicles can be sold in the European Union, they are tested using this laboratory-based test cycle by a national technical service in accordance with EU legislation. The national approval authority grants approval on the basis of these tests. The manufacturer may make an application for approval in any EU country. Once approved in one EU country, all vehicles of its type may be registered throughout the EU. Vehicles are sampled from the production line according to the industry standard of statistical sampling procedures. Those vehicles are tested to ensure they meet the approved requirements.
When a new emissions standard enters into force in the EU (for example, Euro 6 from 1 September 2014 for new types of cars), a manufacturer has a period of one year until all of its future production would have to meet this standard (in this case 1 September 2015 for Euro 6). The regulation also requires checks on the ‘in-service conformity’ of vehicles in use on the road, to ensure that the vehicle will not diverge from the standard when released in the streets.
The old lab test – called the New European Driving Cycle (NEDC) – was designed in the 1980s and became outdated today due to several evolutions in technology and driving conditions.
- Contrary to the technology used for the new WLTP test cycle, which is based on real-driving data, the old NEDC test determined values based on a theoretical driving profile. Moreover, the impact of the presence of optional features on the CO2 and fuel performance of a car was not considered under NEDC.
- Driving has also changed since the 1980s with increased traffic congestion, resulting in more inefficient driving. Additionally, people’s driving styles have also changed. In some countries new car sales are driven by company cars whose drivers receive a fuel card and who probably do not see fuel economy as their highest priority. Simply put, NEDC wasn’t representative of today’s driving profiles anymore.
The old NEDC lab test has been replaced by a more modern and representative laboratory test cycle and procedure: the Worldwide Harmonised Light Vehicle Test Procedure (WLTP).