The WLTP Will Test Cars In More Realistic Situations
New emissions testing comes into force within 12 months
There has been considerable controversy around the inaccuracy of claimed emission levels for many current generation cars, to the extent that there is a widespread belief that the whole testing regime has become devalued.
Current emissions tests carried out under laboratory conditions, called the New European Driving Cycle (NEDC), have been shown to be inaccurate and outdated, having originally been designed in the 1980s.
The European Union has therefore developed a new test, called the Worldwide Harmonised Light Vehicle Test Procedure (WLTP) under which testing conditions will become much more realistic.
While the old NEDC test determined values based on a theoretical driving profile, the WLTP cycle has been developed using real-driving data, gathered from around the world to better represent every-day, more realistic driving profiles.
When does the new Worldwide Harmonised Light Vehicle Test Procedure come into force?
The transition to the WLTP will happen in phases and the new test will officially apply to new types of cars that are introduced to the market for the first time from this September.
Manufacturers may already start requesting WLTP approvals for new car types when the legislation comes into force in the EU which should be any time now.
The WLTP itself will then apply to all new car registrations from September next year.
However, EU measures for end-of-series cars allow for a limited number of unsold vehicles in stock that were approved under the old NEDC test to be sold the following year, that is until September 2019.
The EU has set the most challenging CO2 emission reduction targets in the world. Average CO2 emissions were 186g/km in 1995. Ten years later they had fallen 42% to 161g/km and by 2021 they are targeted to fall by a further 51% to 95g/km. The need for accurate testing is paramount, therefore.
How does the WLTP work?
The WLTP driving cycle is divided into four parts with different average speeds: low, medium, high and extra high.
Each part contains a variety of driving phases, such as stopping, acceleration and braking. For a certain car type, each powertrain configuration is tested with the WLTP for the car’s lightest (most economical) and heaviest (least economical) version.
The Worldwide Harmonised Light Vehicle Test Procedure will introduce much more realistic testing conditions. These include:
- More realistic driving behaviour
- A greater range of driving situations (urban, suburban, main road, motorway)
- Longer test distances
- More realistic ambient temperatures, closer to the European average
- Higher average and maximum speeds
- Higher average and maximum drive power
- More dynamic and representative accelerations and decelerations
- Shorter stops
- Stricter car set-up and measurement conditions.
Because of these improvements, the WLTP will provide a much more accurate basis for calculating a car’s fuel consumption and emissions. This will ensure that lab measurements better reflect the on-road performance of a car.
Even though WLTP will be more accurate, it will not cover all variations globally – and certainly not each individual driving style. There will therefore still be a difference between emissions measured in lab conditions and the real world, as driving behaviour, traffic and weather conditions will continue to differ from one country to another.
New on-the-road testing
The new WLTP test will be complemented by another test called the ‘Real Driving Emissions’ (RDE) test, which will ensure that vehicles deliver low pollutant emissions, not just in the laboratory but also out on the road.
RDE testing of cars on real roads under realistic driving conditions will be a new addition to the existing testing requirements, making Europe the only region in the world to implement such an in-depth testing.
Taking place on real roads, the RDE test will complement the lab tests by measuring what a car delivers in terms of pollutant emissions, such as NOx, while being driven out on the road.
How will RDE testing work?
Under RDE, a car will be driven on public roads and over a wide range of different conditions. Specific equipment installed on the vehicle will collect data to verify that legislative caps for pollutants such as NOx are not exceeded.
Conditions will include:
- low and high altitudes
- year-round temperatures
- additional vehicle payload
- up- and down-hill driving
- urban roads (low speed)
- rural roads (medium speed)
- motorways (high speed)
The RDE test will be implemented this September for all new types of cars and will apply for all registrations from September 2019.
The RDE test will mean that nearly all diesel vehicles will have to be fitted with selective catalytic reduction (SCR) systems and some lean-NOx systems as well.
This will mean additional costs for car manufacturers and smaller cars may not be able to accommodate the fitting of SCR equipment, while some potential owners may be deterred by the extra costs.
Where can I find more details?
ACEA, the umbrella trade association representing the European automotive industry, has launched a new website to provide a greater insight into the various vehicle emissions tests that are coming into force within the next two years.
The new CarEmissionsTestingFacts.eu website provides a fact-based overview on everything related to the testing of car emissions in Europe, including the UK.