NEDC

The New European Driving Cycle was a standardized laboratory test procedure used to measure fuel consumption and emissions from passenger cars in Europe from 1992 to 2018. It consisted of two parts: an urban cycle of about 4 kilometers at low speed, followed by an extra-urban cycle of about 7 kilometers at higher speed, run back-to-back on a dynamometer (a stationary rolling road that measures power output and resistance). Total test time was around 20 minutes.

The urban phase simulated city driving with 13 acceleration and braking events, reaching a maximum speed of 50 km/h. The extra-urban phase included sustained cruising at up to 120 km/h. Crucially, the NEDC allowed considerable idle time and was conducted at a fixed ambient temperature, typically 20 to 25 degrees Celsius. The test measured tailpipe emissions of carbon dioxide (CO2), nitrogen oxides (NOx), particulates, and hydrocarbons, which manufacturers used to declare the car's official fuel consumption figure.

Why it became unreliable

By the 2000s, the NEDC had become notorious for overestimating real-world efficiency. Real driving typically produces 20 to 40 percent higher emissions than NEDC results predicted, partly because the test cycle's gentle acceleration profiles and predictable pattern allowed manufacturers to tune engine management systems to perform optimally during testing while sacrificing efficiency in actual use. The low maximum speed and lack of motorway driving at sustained high load also skewed results toward lighter, lower-power vehicles.

The NEDC was superseded in 2018 by the Worldwide Harmonised Light Vehicle Test Procedure (WLTP), which uses longer, more aggressive driving patterns, variable ambient temperatures, and includes roof racks and other load variations. However, NEDC remains relevant to anyone reviewing pre-2018 vehicle specifications or comparing historical emissions data, and it established the framework for how European automotive regulation continues to be written today.