What is WLTP and how does it work?
Under conditions defined by EU law, the Worldwide Harmonised Light Vehicle Test Procedure (WLTP) laboratory test is used to measure fuel consumption and CO2 emissions from passenger cars, as well as their pollutant emissions.
The old lab test – called the New European Driving Cycle (NEDC) – was designed in the 1980s. Due to evolutions in technology and driving conditions, it became outdated.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 welcomes the shift to WLTP and has actively contributed to the development of this new test cycle.
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: low, medium, high and 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) version.
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 European Union and other regions will apply the test in different ways depending on their road traffic laws and needs.
What are the benefits of WLTP?
The Worldwide Harmonised Light Vehicle Test Procedure (WLTP) is the new laboratory test for measuring fuel consumption and emissions from cars.
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.
WLTP 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;
- Optional equipment: CO2 values and fuel consumption are provided for individual vehicles as built;
- Stricter car set-up and measurement conditions;
- Enables best and worst-case values on consumer information, reflecting the options available for similar car models.
From NEDC to WLTP: What will change?
As of September 2017, the old NEDC lab test for cars will gradually be replaced by the new WLTP test (Worldwide Harmonised Light Vehicle Test Procedure). What will change exactly?
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.
The European Union has therefore prepared a new test, called the Worldwide Harmonised Light Vehicle Test Procedure (WLTP) that applies from September 2017.
The same car suddenly has two different CO2 values, why is this?
The new Worldwide Harmonised Light Vehicle Test Procedure (WLTP) is a new and more robust test cycle for cars, and therefore has higher (but more realistic) CO2 and fuel consumption values.
Before September 2017, all cars at dealerships had CO2 values based on the old NEDC test (the New European Driving Cycle).
During the period of transition from NEDC to WLTP that started in September 2017, cars approved before then will continue to have CO2 values as measured under the NEDC test only.
However, when a new car type is certified under WLTP after September 2017, its official vehicle documents (the Certificate of Conformity) will have CO2 emission values from both the new lab test as well as the old one.
From September 2018, all new cars must have WLTP-CO2 values
This means that after September 2017, when the switch from the NEDC to WLTP is being made, one might come across two different values for the same car. This risks being quite confusing, making it difficult to compare cars.
A very important issue therefore is how WLTP will be integrated in car labelling and other consumer information.
Will my fuel consumption increase under WLTP?
Practically, your car’s fuel consumption performance will not change with these new WLTP values. The Worldwide Harmonised Light Vehicle Test Procedure will result in a higher g/km CO2 value for the one and same vehicle compared to NEDC, simply because it is a more rigorous and longer test – meaning the WLTP will provide a better reflection of today’s situation than the NEDC. In other words, the higher CO2 value does not mean increased fuel consumption, but rather a more realistic CO2 value due to the change in how the vehicles are tested.
Will the WLTP test affect CO2 targets?
The CO2 targets that car manufacturers have to meet by 2021 are based on the old NEDC test, the so-called New European Driving Cycle. From the introduction of the new WLTP test in September 2017, the WLTP-CO2 values will be translated back to NEDC-equivalent values to monitor compliance against the CO2 targets set by the European Union
A ‘correlation exercise’ was carried out by the European Commission to determine how the values for new cars measured on the WLTP cycle will be translated back to NEDC equivalent values for monitoring against the EU CO2 targets. Given that the European Commission has tightened the test conditions for NEDC, it will be more challenging for manufacturers to meet their targets.
A comparison of new WLTP-CO2 values and NEDC CO2 values over the period of transition from NEDC to WLTP will be the basis for the European Commission to calculate WLTP-specific targets for 2020. These revised targets are required by EU legislation to be of ‘comparable stringency’ to the current CO2 targets based on the NEDC test.
Then, as of 2020, the member states and the European Commission will start to monitor the WLTP values of new cars against manufacturers’ new CO2 target values based on the Worldwide Harmonised Light Vehicle Test Procedure (WLTP).
Source: WLTP Facts
Key dates, introduction and timings of the new economy regs:
All brand new cars being homologated for launch must now meet the new WLTP rules, but there is a staggered roll-out. The WLTP laboratory element of the tests will have been conducted on all models on sale by 1 September 2018, while the on-road Real Driving Emissions (RDE) testing element must have been completed by 1 September 2019.
From 1st April 2020 it’s likely that the new figures will be the ones used for tax purposes and published in marketing. Following this, 2021 will see WLTP figures finally killing off their NEDC predecessors.
Why the two-year delay in launching the new regulations in full? Because of the enormous complexity of testing every make, model, bodystyle and derivative, complete with every accessory and optional extra. The new rules demand transparency on what effect, for example, fitting bigger alloy wheels will have on your CO2 and mpg.