NEDC

The New European Driving Cycle, universally abbreviated to NEDC, was the laboratory test procedure used across Europe for decades to measure a car's fuel economy, carbon-dioxide output and regulated pollutant emissions. Its purpose was to provide a single, repeatable standard so that every new model was assessed identically, allowing official figures to be compared and emissions limits to be enforced. For many years the NEDC number on a brochure was the headline economy figure that buyers relied upon.

The procedure was conducted on a rolling road, or chassis dynamometer, in a controlled laboratory rather than on real roads. It consisted of a repeated urban cycle followed by a single extra-urban phase, with the whole test lasting only around twenty minutes and covering roughly eleven kilometres. Speeds were modest, accelerations gentle and steady-state cruising was common, with a top speed of just 120 km/h reached only briefly.

The roots of the cycle lay in the 1980s, and this is central to understanding its shortcomings. It was designed for an era of less powerful cars and lighter traffic, and its sedate, idealised speed trace bore little resemblance to how modern vehicles are actually driven. Manufacturers were also permitted to exploit numerous tolerances and optimisations during testing, such as taping up panel gaps, over-inflating tyres, disconnecting ancillary loads and running cars at the most favourable permitted weight.

The consequence was a growing and well-documented gap between official and real-world figures. Quoted fuel economy was frequently optimistic by twenty to forty per cent, and the divergence widened over the years as the test failed to keep pace with vehicle technology, including the increasing fitment of fuel-saving features whose benefit appeared on the cycle but not always on the road. This eroded public trust in the numbers and made it harder for drivers to budget accurately for fuel.

The NEDC's credibility was further undermined by the realisation that laboratory testing alone could be gamed, exposed most starkly by the diesel-emissions scandal. In response, regulators replaced it. From 2017 to 2019 the more rigorous Worldwide Harmonised Light Vehicles Test Procedure, or WLTP, was phased in for measuring economy and carbon dioxide, supported by on-road Real Driving Emissions testing for pollutants such as NOx.

NEDC therefore now belongs largely to history, though figures derived from it persisted on some documents and in certain tax calculations during the transition. It is best understood as the predecessor against which WLTP and RDE are defined: an early, well-intentioned but ultimately unrepresentative attempt to quantify how clean and economical a car really is.