WLTP vs NEDC & Euro 6.1 vs Euro 6.2

The old NEDC (New European Driving Cycle) is being replaced by the new WLTP (Worldwide Harmonized Light Vehicles Test Procedures) which is a longer cycle more representative of real world driving. The economy figures obtained from WLTP are more reflective of customers’ actual experience.

Additionally vehicles also need to prove their air quality credentials by passing the RDE (Real Driving Emissions) test. This is done by using sensitive analysis equipment to the trace tailpipe emissions of pollutants, including NOX and particulates, while the car is driven in a wide range of both every-day and extreme conditions.

What is NEDC?​

NEDC = New European Driving Cycle and was the official emissions test

This is a laboratory test in strict conditions monitored by a government-appointed independent approval agency (VCA). It was first introduced in 1992 and is based on a theoretical driving profile. It has two parts -the first simulates city traffic with many stop/start phases, and the second corresponds to an extra-urban journey at a maximum speed of almost 75 mph

It allows fuel consumption comparison of different vehicles. However it doesn’t reflect the fuel consumption of day-to-day driving, and hence real consumption can be very different.

What is WLTP?

WLTP = Worldwide Harmonized Light Vehicles Test Procedures and is the new test cycle that replaces NEDC.

This is also laboratory test but is based on a global statistical survey of real driving profiles. It has four parts with different average speeds: low, medium, high and extra high. Each phase includes different amounts and degrees of acceleration, braking and stopping, all to simulate everyday driving.

WLTP results in higher CO2and consumption figures but the values will be more realistic to real world experience. WLTP also takes into consideration option content and this generates dependent and unique CO2and consumption figures.

Click here to see new WLTP Driving Cycle figures for Vauxhall Astra and Vauxhall Insignia

WLTP means that the economy figures become more reflective and consistent with driving experience, but the additional requirement of the real world evaluation (RDE) ensures a greater transparency.

This will result in official economy figures increasing as their parity to the real world becomes more consistent.

Real Driving Emissions

​Real Driving Emissions (RDE) works by fitting equipment called a Portable Emissions Measurement System (PEMS) to the vehicle, which measures emissions while the vehicle is driven on the road.

Given the huge differences in temperature, road and vehicle conditions as well as driving styles, no lab test can ever replicate exactly what happens on the road. RDE testing will demonstrate that new cars’ low emissions are achieved in these real world conditions.

RDE will also include some extreme driving conditions, rarely encountered by most motorists, for example carrying a heavy load up a steep hill at high speed in very low temperatures.

NEDC and BIK Backdating

Until 6th April 2020 (SMMT Proposal), VED/BIK will continue to be determined using a NEDC-type value. Since the NEDC cycle has been replaced, this figure will be “back-correlated”or calculated from approved WLTP datausing COMPAS (an EU Commission Tool supported by ACEA).

The back-correlated NEDC CO2 does not take into consideration option content, and therefore options (except tyres) will not effect VED/BIK until 6th April 2020.

Additionally the CAFE (Corporate Average Fuel Economy) 2020 target will not change, and will continue to be monitored using “back-correlated” NEDC.

When does WLTP come in to force?

1st September 2017

  • Euro 6d TEMP (Euro6.2) is required for all new types of cars (Cat-M1)

1st September 2018

  • Euro 6d TEMP (Euro6.2) is required for all new registrations of cars. End-of-series derogation is approved but is more restricted than previously.

1st January 2019 [SMMT proposed date]

  • WLTP economy data used in all communication including advertising

6th April 2020 [SMMT proposed date]

  • HMRC start using WLTP economy data for VED and BIK.

SMMTproposed dates took into consideration industry consultation to which Vauxhall contributed. Dates are currently with Ministry for approval.