WLTP. All you need to know.

The acronym WLTP is short for "worldwide harmonized light vehicle test procedure" and it represents a test method to determine vehicles' consumption and emission values. It is being gradually introduced from 1 September 2017 to replace the previous NEDC test method. Thanks to its dynamic configuration, it is significantly closer to actual driving characteristics than the previously used method.

WLTP is characterised by significantly higher accelerations and a much more dynamic driving profile. The top speed is raised to 131 km/h and the average speed increases to 47 km/h.

The driving time is extended by 10 minutes, the proportion of motorway journeys increases and times when the vehicle is at standstill are reduced. The distance driven is extended to 23 kilometres. Gearshift times are calculated in advance, specifically for each vehicle and drivetrain.

In future, all optional extras influencing vehicle aerodynamics, rolling resistance or vehicle mass will be taken into account in the assessment. The power consumption of optional extras will also lead to increased CO2 values. The air conditioning is the only exception in the first stage of the WLTP.

NEDC (new European driving cycle) is the current test cycle for passenger cars. The first European test cycle came into force in 1970 with the objective of providing values that were comparable and reproducible across all manufacturers. In 1992 it was extended beyond urban traffic situations.

At 34 km/h, the average speed of the NEDC is low, as are the acceleration specifications and the top speed of 120 km/h. The composition of the cycle is not representative of the average journeys taken by customers. The energy consumption of optional equipment and convenience functions, such as the air conditioning system, radio or seat heating are also not included in the measurement.

In the case of vehicles with manual transmissions no vehicle-specific parameters are taken into account when determining the shift timing points. This can result in large differences in consumption compared with everyday driving conditions. As a result, NEDC no longer provides a transparent representation of real consumption figures.

RDE is short for real driving emissions and represents an on-road test to verify pollutant emissions. It describes vehicles' on-road emission response in real conditions. Exhaust gas measurement for the purposes of model series authorisations used to be performed at test stations only. Since March 2016, testing has also taken place in real world conditions to be more representative of customers’ everyday driving experiences.

A PEMS unit (portable emissions measurement system) is used to determine nitrogen oxide (NOx) and carbon monoxide emissions (CO). At a later point particulate emissions will also be determined. In this process, there is no defined cycle and test drives as well as measurements are carried out in real, everyday traffic situations in compliance with the highway code. Vehicles are driven on public roads for between 90 and 120 minutes, one third each in urban environments, extra-urban environments and on motorways.

In urban environments the intended average speed is between 15 km/h and 30 km/h, on motorways between 90 km/h and a minimum of 110 km/h, but no faster than 145 km/h. The ambient temperature must be between 0 and 30° and the air conditioning system must be on. Test drives must not be carried out at altitudes above 700 metres above sea level and they must feature a maximum of 100 metres difference in altitude.

From September 2017 Euro 6 emission limit values must be complied with during RDE cycles. In the first step this applies to models to be newly certified from 1 September 2017 and from 1 September 2019 at the latest for all models.

Requesting RDE results

RDE results of Mercedes-Benz vehicles, determined by Mercedes-Benz as the manufacturer as well as by independent, officially certified, technical service providers, can be requested using a contact form stating the PEMS test range of the corresponding Mercedes-Benz vehicle.

The PEMS test range number associated with the vehicle is available from the homepage of the European Automobile Manufacturers Association (ACEA).

In contrast to NEDC, the WLTP driving cycle is ten minutes longer and requires the vehicle to be stationary for 13 percent of the test. The entire cycle covers 23.5 kilometres – more than double the NEDC. It features higher average speeds of up to 131 km/h, exposes vehicles to higher fluctuations in speed and is subject to significantly more stringent test specifications.

The introduction of WLTP creates more transparency in terms of fuel consumption. Customers will receive a more realistic, comparative benchmark for consumption and emission figures of different vehicle models.

CO2 and consumption values will also change as a result of different testing procedures, a technically identical vehicle will produce numerically higher CO2 and consumption values.

In future, customers will be able to determine the CO2 values of their vehicle model much more accurately as a result of the choice of optional extras. Mercedes-Benz is actively engaged in the introduction of WLTP and will provide Retailers and customers with all the information they need to ensure a smooth transition between testing procedures.

The data will also include a new type of equipment-specific indication: from the model with the lowest energy requirement to the model version with the highest. Numerically, this spread stretches from "WLTP low" (minimum optional extras) to "WLTP high" (maximum optional extras).