In our modern world, vehicle fuel consumption and emissions are becoming more and more important.

So, the ‘Worldwide Harmonised Light Vehicle Test Procedure’ or WLTP has been designed by the European Union to provide more realistic testing conditions to calculate both of these.

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. The current lab test – called the New European Driving Cycle or NEDC was developed in the 1980s, but since the way we drive and the vehicles we use have changed so much since then, some new way of measuring fuel consumption and emissions was needed.

With the WLTP, the driving cycle is divided into four sections taking into account different average speeds. These are low, medium, high and extra high. Each section contains a variety of driving phases, including stopping, acceleration and braking. For each new vehicle type, every powertrain configuration is tested under the WLTP for the car’s lightest and heaviest variants.

Real Driving Emission Tests The Real Driving Emission or RDE tests, measure the levels of pollutants such as NOx emitted by cars while driven on the road. The RDE tests will be run alongside current NEDC and future WLTP test cycles as a validation process. RDE ensures the delivery of low emissions from vehicles during on-road conditions throughout Europe.

The RDE test is performed as part of emissions type approval on public roads in real traffic, using a Portable Emissions Measurement System or PEMS. Initially, only NOX and particulate number emissions are included in binding limits. The initial diesel RDE limit for NOx is 168 mg/km, which, for all new vehicle types, came into force on 1 September 2017.