What is WLTP and how does it work?
In the 19080’s the old lab test which was called the New European Driving Cycle (NEDC) was designed. Due to the evolutions in technology and driving conditions, it became outdated. The European Union has therefore developed a new test, called the Worldwide Harmonised Light Vehicle Test Procedure (WLTP). The EU automobile industry welcomed the shift to WLTP and has actively contributed to the development of this new test cycle.
Most cars on sale in Britain today miss their claimed combined fuel economy figures – the ones quoted by manufacturers in adverts – by a quarter or worse. The NEDC regs were last updated in 1997.
While the old NEDC test determined test values based on a “theoretical driving profile”, the WLTP cycle was developed using “real-driving data”, gathered from around the world. WLTP therefore better represents everyday driving profiles.
The WLTP driving cycle is divided into four parts with different average speeds:
- Extra high
Each part contains a variety of driving phases, stops, acceleration and braking phases. For a certain car type, each powertrain configuration is tested with WLTP for the car’s lightest (most economical) and heaviest (least economical) versions.
WLTP was developed with the aim of being used as a global test cycle across different world regions, so pollutant and CO2 emissions as well as fuel consumption values would be comparable worldwide. However, while the WLTP has a common global core, the EU and other regions will apply the test in different ways depending on their road traffic laws and needs.
Will WLTP end the discrepancy between the laboratory and on-road performance of cars?
Even though the Worldwide Harmonised Light Vehicle Test Procedure (WLTP) will provide a far more realistic representation of conditions encountered on the road than the old NEDC lab test (New European Driving Cycle), it will not cover all possible variations. Moreover, each individual driver will continue to have a different driving style: one driver might accelerate faster, take corners faster or brake more suddenly than another who might drive more conservatively.
Given that driving behaviour, traffic and weather conditions will continue to differ from one country to another, there will still be a difference between emissions measured in lab conditions and the real world. However, as there is no single real-world emission value, only values obtained by standardised laboratory tests allow us to directly compare the emissions and fuel consumption of different car models from different car manufacturers.
When will the WLTP changes take place?
- WLTP will officially apply to all new cars from September 2017. New type of cars are models which are introduced on the market for the first time.
- Manufacturers may start requesting WLTP approvals for new car types when the legislation comes into force in the European Union (No sooner than end of July 2017)
- WLTP will apply to all new registrations from September 2018
- EU Measures for “end-of-series” cars allow for a limited number of unsold vehicles in stock that were approved under the old test (NEDC) to be sold by September 2019
Transition Timeline: From NEDC to WLTP
|From September 2017|
- Cars type approved using NEDC before September 2017 can still be sold.
- WLTP type approval testing will be introduced for new car types.
- Some cars will have ‘old’ NEDC values, while others will already be certified under the new WLTP conditions.
- The industry would like to start using WLTP-based results for general consumer information (eg sales brochures and websites).
- During the period of transition (up until the end of 2018), only NEDC values should be used on labels and information in dealerships to enable consumers to compare different cars.
- It is expected that national tax regulations will continue to be based on NEDC values
|From September 2018|
- All new cars must be tested according to the WLTP test, and no longer on NEDC
|From September 2019|
- All cars in dealerships should have WLTP-CO2 values only to avoid any confusion among consumers, in the view of the automobile industry.
- An exception will be made for end-of-series vehicles to allow for a limited number of unsold vehicles in stock that were approved under the old NEDC test to be sold for one more year.
- National governments should adjust vehicle taxation and fiscal incentives to WLTP values, respecting the principle that WLTP should not have a negative impact on consumers.
Main Differnances Between The Two Test Procedures
|Test cycle||Single test cycle||Dynamic cycle more representative of real driving|
|Cycle time||20 Minutes||30 minutes|
|Cycle distance||11 kilometre||23.25 kilometre|
|Driving phases||2 phases, 66% urban and 34% non-urban driving||4 more dynamic phases, 52% urban and 48% non-urban|
|Average speed||34 kilometre per hour||46.5 kilometre per hour|
|Maximum speed||120 kilometre per hour||131 kilometre per hour|
|Influence of optional equipment||Impact on CO2 and fuel performance not considered under NEDC||Additional features (which can differ per car) are taken into account|
|Gear shifts||Vehicles have fixed gear shift points||Different gear shift points for each vehicle|
|Test temperatures||Measurements at 20-30°C||Measurements at 23°C, CO2 values corrected to 14°C|
What will be the main benefits of WLTP ?
WLTP will introduce much more realistic testing conditions. These will include:
- More realistic driving behaviour
- A greater range of driving situations which will include urban, suburban, main road, motorway
- More realistic ambient temperatures, closer to the European average
- Optional equipment: CO2 values and fuel consumption are provided for individual vehicles as built
- Higher average and maximum speeds
- Higher average and maximum drive power
- Shorter stops
- More dynamic and representative accelerations and decelerations
- Longer test distances
- Enables best and worst-case values on consumer information, reflecting the options available for similar car models.
- Stricter car set-up and measurement conditions
Because of all these improvements, 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.