The Worldwide harmonised Light vehicles Test Procedure – the acronym for which is WLTP – is the name being given to the new vehicle test procedure that replaces the long-established New European Driving Cycle (NEDC).
WLTP is being introduced in two phases:
- From September for all new car and van models requiring a new type approval number
- From September 2018 for all cars and vans
The results of WLTP MPG and emissions testing is that, in most cases, official vehicle MPG figures will be worse than equivalent NEDC figures, while CO2 emissions figures will be higher.
Regarding vehicle-related taxes – company car benefit-in-kind tax, Vehicle Excise Duty and capital allowances – currently linked to the NEDC test, HM Treasury has yet to decide when to link the tax system to WLTP data. Industry speculation suggests that 2020/21 could be the financial year for changes to be introduced.
An HM Treasury spokesman said: “We will look to agree a suitable moment to move the tax system from NEDC to WLTP, based on industry input.”
However, industry experts have suggested that CO2 figures on a car-by-car basis could increase by about 20% with introduction of the WLTP.
The British Vehicle Rental and Leasing Association is also warning that under WLTP testing, optional equipment is likely to have a “more significant” impact than under the NEDC regime and therefore further increase the cost and tax implications.
During a transitional period between September 2017 and September 2020, the certificate of conformity issued by the Vehicle Certification Agency will show both WLTP and NEDC CO2 values. From 2020 new vehicles will only be tested using WLTP type approval procedure. However, it is not clear yet when the Driver and Vehicle Licensing Agency will start recording the new WLTP figure on V5 vehicle registration documents, or if it will record both WLTP and NEDC figures.
Vauxhall has published comparison figures for some models tested under both the NEDC and WLTP cycles.
The results show, for example:
- Vauxhall Astra hatchback 100PS 5speed manual – WLTP 52.3mpg, NEDC 67.3mpg (difference 15mpg)
- Vauxhall Astra hatchback 1.6 CDTi 110PS 6speed manual – WLTP 65.7mpg, NEDC 85.6mpg (difference 19.9mpg)
- Vauxhall Insignia Sports Tourer 1.5 turbo ecoFLEX 140bhp 6speed manual front wheel drive – WLTP 49.5mpg, NEDC 57.6mpg (difference 8.1mpg)
- Vauxhall Insignia Sports Tourer 2.0 Turbo D 170bhp 6speed manual front wheel drive – WLTP 60.1mpg, NEDC 64.2mpg (difference 4.1mpg).
Meanwhile, PSA, the French company behind the Citroen, DS and Peugeot brands, has made independent, certified calculations of real-world fuel consumption of vehicles travelling along a 57.3 mile route combining urban, rural and motorway driving available to customers.
The vehicles tested travel on open routes in ‘normal’ traffic conditions, with passengers and luggage. The use of air conditioning or heating was also mandatory.
The results show, for example:
- Citroen C4 Picasso BlueHDI 100 Feel 5dr – PSA test, 49.56mpg, NEDC 74.3mpg (difference 24.74mpg)
- Citroen C4 Cactus 1.6 BlueHDI Feel 5dr – PSA test 56.5mpg, NEDC 78.5mpg (difference 22mpg)
- Peugeot 208 1.2 PureTech 82 Allure 5dr – PSA test 43.5mpg, NEDC 62.8mpg (difference 19.3mpg)
- Peugeot 3008 1.6 Blue HDI 120 Active 5dr – PSA test 46.3mpg, NEDC 70.6mpg (difference 24.3mpg).
Real-world MPG figures for other models in the PSA range are available at:
Manufacturers have yet to give indicative NEDC and WLTP comparisons for CO2 emissions. PSA said it was planning to publish CO2 data based on WLTP tests in early 2019.
Both NEDC and WLTP test cycles are carried out under laboratory conditions, but the WLTP test cycle has been reformulated to be more representative of ‘real world’ driving taking into account higher speeds and loads, more dynamic acceleration and fewer and shorter stop phases. As a result, WLTP fuel consumption is measured over four different speeds, compared with three for the NEDC test.
There is currently no WLTP test available for plug-in hybrid vehicles. Those models will continue to be tested against the NEDC standard until a new test has been formulated and approved.
What’s more, Euro6 diesel engine vehicles will also be tested using the so-called Real Driving Emissions (RDE) procedure. It will complement the WLTP test and check levels of nitrogen oxides (NOx) and particle numbers (PN), measured during the laboratory test and confirm them in ‘real driving’ conditions. The RDE does not measure CO2 emissions.
The new WLTP test is being introduced because of concern at the growing gap between published MPG figures, and therefore CO2 emission figures, for new vehicles and their in-life performance.
Consultancy, Emission Analytics publishes its EQUA Index, which features fuel consumption, carbon dioxide, carbon monoxide and nitrogen oxide figures on more than 60,000 vehicles. It recently claimed that average CO2 emissions from new petrol cars had fallen by 6% since 2012, when it started collecting data. However, over the same period, the average emissions from diesel cars had risen by 5%.
Claimed to be “drastically” more realistic than even the new WLTP, Nick Molden, CEO and founder of Emissions Analytics, said: “In recent years, we have been kidding ourselves about our actual achievement in reducing CO2 from cars. Encouraging official data has given a misleadingly positive impression. The new official WLTP will help close the gap, but only partially.”