A NEW way of measuring fuel economy for cars has come into force.
The new tests replace a regime that has not been updated for some 20 years and is designed to give motorists a realistic picture of fuel consumption in everyday use.
Under the regulations, all new cars sold in the UK will have to be tested on the road instead of only under laboratory conditions.
For years drivers have known that the so-called official fuel economy figures for their cars bore little resemblance to what they actually achieved.
The scenario was clouded by the VW emissions scandal which revealed test programmes could be fiddled to show false readings.
As of September 1, every new car destined for UK showrooms will need to undergo a new test called the Worldwide Harmonised Light Vehicle Test Procedure (WLTP), which measures all regulated emissions, as well as CO2and fuel economy.
And in a world first, new models being developed for sale in Britain will also need to prove their air quality credentials by passing a brand new Real Driving Emissions (RDE) test using special state-of-the-art portable emissions measurement (PEMS) equipment.
This very sensitive equipment analyses the trace tailpipe emissions of pollutants, including NOXand particulates, while the car is driven in a wide range of both every-day and extreme conditions.
It is designed to ensure vehicles meet the tough Euro 6 emissions standard on the road as well as in the lab where the WLTP evaluation will still be carried out.
Mike Hawes, chief executive of the Society of Motor Manufacturers and Traderssaid: "These new and demanding tests will soon give consumers emissions performance information that is far closer to what they experience behind the wheel - and inspire greater confidence that the new cars they buy are not only the cleanest, but the most fuel efficient ever produced."
He added: "We welcome this challenging new regime, which will provide hard evidence that the industry's ongoing investment in ever more advanced technology is delivering on air quality goals."
A number of car companies, including Ford, Vauxhall and Audi have recently introduced ‘scrappage' schemes offering huge discounts on new models to owners who trade in vehicles which do not comply with the latest emission standards.
Sales of diesel cars have also slumped in the past few months as concerns grow over air pollution.
The WLTP and RDE tests replace the previous and long-outdated laboratory test known as the New European Driving Cycle (NEDC), which was designed back in the 1980s and last updated in 1997.
Revolutionary in its day, NEDC was intended to provide consistent benchmarking information for buyers across Europe as well as determining whether cars meet minimum air quality standards.
It also provided the basis for the UK's CO2 based Vehicle Excise Duty system which was updated in April this year, setting new emission thresholds for the next four years.
The WLDC process analyses a vehicle's performance over a longer distance and time, at higher average speeds and also includes variations in gearing and more rapid acceleration and deceleration patterns.
It will be carried out on all new models including electric vehicle and plug-in hybrids.
While that test will still be done under controlled conditions, it will be complemented by the on-road RDE test which will ensure the vehicle's lab test performance is matched in everyday conditions.
It uses a portable system attached to the exhaust which measures emissions while the vehicle is driven on the road.
Some car makers, notably Peugeot, have already been carrying out such testing and publishing the data.
RDE will also include 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.
Only when a vehicle meets these requirements, as independently witnessed by a government-appointed independent approval agency, will it be approved for sale in Europe.
The new tests are part of European regulations designed to improve air quality and tackle climate change.