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Glossary Of Terms

This glossary is designed to give definitions to words and abbreviations you might have come across whilst using this website.



Allgemeiner Deutscher Automobil-Club is the General German Automobile Club and is Europe's largest motoring association, rather like the UK's AA, RAC or Green Flag except much bigger.


Conformity Factor - a conformity factor is the emissions limit that applies to on-road emissions testing, due to start in 2017. It is set slightly higher than the lab-test limit to allow a margin for inaccuracy of the measuring equipment during on the road driving.


Diesel Particulate Filter -a diesel particulate filter is fitted to the exhaust of all Euro 5 and Euro 6 diesel cars. It traps 99% of all particulates before they leave the tailpipe, virtually eliminating emissions of exhaust particulate matter compared with older cars.


Exhaust Gas Recirculation - EGR is a technology used to reduce the levels of NOx emitted by the engine. It involves recirculating some hot exhaust gas back into the engine combustion chamber. This reduces the amount of oxygen, and lowers combustion temperature. Less oxygen and a lower combustion temperature reduces the amount of NOx emitted by a vehicle.


Environmental Protection Agency, contrary to popular belief is not the correct name for the agency responsible for the environment in the UK, it is in fact the Environment Agency (AE)


Extra Urban Driving Cycles

Euro 6

Euro 6 (referred to as Euro VI for heavy commercial vehicles) is the most recent regulation for vehicles sold in Europe to ensure the cleanest engines. Since 1993, the European Commission has enforced a Euro standard of emissions, which all vehicles on sale must meet.


New European Driving Cycle - the NEDC is the old EU’s official laboratory test of the air quality and CO2 emissions of new vehicles. Originally developed in the 1970s. Subsequently replaced with the WLTP.


Nitric Oxide, a colourless gas. One of the by-products of burning fuel. Part of NOx.


Nitrous Oxide (also known as NOS). More commonly known as laughing gas. It’s a colourless gas with a slightly sweet odour and taste. Also known as ‘Hippy Crack’, breathing Nitrous Oxide can cause dizziness, unconsciousness, and even death. It is used to numb pain during dental procedures, in engines to increase their power output (made famous in films like Fast & Furious), and in whipped cream aerosol cans to prevent the cream from going ‘bad’. Part of NOx


The term 'Nitrogen Oxides' (NOx) is used to describe a group of gasses including Nitric Oxide (NO), which is a colourless, odourless gas and Nitrogen Dioxide (NO2), which is a reddish-brown gas with a bad odour. It also contains N2O, N2O2, N2O3, N2O4, and N2O5


Nitrogen Dioxide appears as a reddish brown gas or yellowish-brown liquid when cooled or compressed. Part of NOx.


Dinitrogen Dioxide is the brown film we see in the atmosphere all over highly polluted cities. Part of NOx.


Dinitrogen Trioxide appears as a blue liquid with a sharp, unpleasant chemical odour. Its vapours are very toxic by inhalation. Part of NOx.


Dinitrogen Tetroxide. Highly Toxic gas. Part of NOx.


Dinitrogen Pentoxide. A white solid, very soluble in water. Part of NOx.


Portable Emissions Measurement system - a sophisticated mobile laboratory in a box, which is fitted to the car and analyses exhaust emissions while the vehicle is driven on the road or a test track.


Particulate matter, commonly known as soot, is a waste material of combustion. Thanks to a diesel particulate filter (DPF) fitted to Euro 5 and Euro 6 diesel cars that captures nearly all the exhaust particulates, this pollutant is all but eliminated.


Real Driving Emissions - the emissions that a car produces on the road rather than in a laboratory environment. On-road emissions can be affected by many different factors, including car and traffic conditions, temperature, weather, road surface and gradient, vehicle load and driving style.


Scottish Environmental Protection Agency is Scotland's principal environmental regulator.


Urban Driving Cycle.


VIN stands for Vehicle Identification Number and it is the unique number stamped onto the chassis of your car. Regardless of whether you change your car’s registration plate, the VIN will always remain unchanged and is ultimately what is used ultimately to identify your vehicle. It has historically been located at the bottom corner of your vehicle’s windscreen, but more recently manufacturers have taken to placing the VIN code elsewhere on the vehicle.


Worldwide harmonized Light-duty Test Cycle.


Worldwide harmonized Light-duty Test Procedure is the test used to measure fuel consumption and pollution from vehicle emissions and replaces the old NEDC standard..