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VED / Car Road Tax is changing.... How does the new April 2020 WLTP car emission test work?

VED / Car Road Tax is changing.... How does the new April 2020 WLTP car emission test work?
26th February 2020
How does the new April 2020 WLTP car emission test work?

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, such as stopping, acceleration and braking.

The Worldwide Harmonised Light Vehicle Test Procedure (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

• Stricter car set-up and measurement conditions.

Because of these improvements, the 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.

Even though WLTP will be more accurate, it will not cover all variations globally – and certainly not each individual driving style. There will therefore still be a difference between emissions measured in lab conditions and the real world, as driving behaviour, traffic and weather conditions will continue to differ from one country to another.

New on-the-road testing

The new WLTP test will be complemented by another test called the ‘Real Driving Emissions’ (RDE) test, which will ensure that vehicles deliver low pollutant emissions, not just in the laboratory but also out on the road.

RDE testing of cars on real roads under realistic driving conditions will be a new addition to the existing testing requirements, making Europe the only region in the world to implement such an in-depth testing.

Taking place on real roads, the RDE test will complement the lab tests by measuring what a car delivers in terms of pollutant emissions, such as NOx, while being driven out on the road.

How will RDE testing work?

Under RDE, a car will be driven on public roads and over a wide range of different conditions. Specific equipment installed on the vehicle will collect data to verify that legislative caps for pollutants such as NOx are not exceeded.

Conditions will include:

• low and high altitudes

• year-round temperatures

• additional vehicle payload

• up- and down-hill driving

• urban roads (low speed)

• rural roads (medium speed)

• motorways (high speed)

The RDE test will mean that nearly all diesel vehicles will have to be fitted with selective catalytic reduction (SCR) systems and some lean-NOx systems as well.

This will mean additional costs for car manufacturers and smaller cars may not be able to accommodate the fitting of SCR equipment, while some potential owners may be deterred by the extra costs.

Of course, you're now wondering what this all means for you. Using the table below, you will be able to calculate which tax band your vehicle would be in if you were to buy it after 1st April 2020.

What Tax Band is my car in? 


  1.   So, if you are thinking of buying a Range Rover Sport 3.0 P400 HST Auto, why not check out our latest offers on this and other alternatives today? You could be saving up to £855 before 1st April 2020.