The EU emissions test
The New European Driving Cycle is a driving cycle consisting of four repeated ECE-15 driving cycles and an Extra-Urban driving cycle, or EUDC. The NEDC is supposed to represent the typical usage of a car in Europe, and is used, among other things, to assess the emission levels of car engines. All these statistics are based on fuel consumption figures from the Vehicle Certification Agency (VCA), which are derived from an EU test procedure prescribed by an amended EU directive and known as the New European Drive Cycle.
This involves a 19 minute test in two parts: the ‘urban cycle’, a series of 12 starts and stops at an average of 12mph and never exceeding 31mph, and the ‘extra urban cycle’, a faster single sequence of acceleration, deceleration and steady-speed driving, never exceeding 75mph. An average of the two parts, weighted by their respective distances, gives the EU combined fuel consumption and CO2 emissions figures.
It's a very precise test, carried out on a rolling road in a laboratory at exactly 20C. It doesn't measure fuel used, but analyses exhaust gases and calculates back for fuel usage and the closely related carbon dioxide emissions. Strangely, car manufacturers are allowed to conduct their own test, which seems a bit like being asked to mark your own exam paper.
The driving is actually done by computer-controlled robots, which press the throttle by the precise amount required to get the car to the prescribed speeds; in fact, they are allowed to slightly undershoot those speeds as a percentage deviation. The car's air-conditioning, heater, lights and radio are not used; there's no headwind; the imaginary road is flat and empty; the ambient temperature is that of a warm summer's evening.
It's also a complete fiction, more worthy of HE Bates' Darling Buds of May than the average winter crawl around the M25 with wipers scraping at the windscreen. Even the "worst-case" Urban cycle figure is seldom an accurate indicator, and the combined figure on which CO2 emission data is based is no more an indication of your real-world fuel consumption than a reading from a gipsy's tea leaves would be