Carbon dioxide (CO2)

When fuels such as petrol and diesel, are combusted carbon dioxide (CO2) is produced and released into the atmosphere. CO2 is believed to be a major contributor to global warming so vehicle makers have been set tough limits to meet by 2020 – 95g/km with further reductions expected by 2030.

Conformity Factor (CF)

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 (DPF)

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)

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 formed.

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.

Lean NOx trap (LNT)

A lean NOx trap or catalyst is an exhaust after-treatment technology, which reduces the emissions of NOx from the tailpipe. It captures NOx and neutralises it in the exhaust system.

New European Driving Cycle (NEDC)

The NEDC is the old EU’s official laboratory test of new cars’ air quality and CO2 emissions. Originally developed in the 1970s and last revised inm it had become outdated both in terms of road and driving conditions and vehicle technology.


NOx refers to nitrogen oxides or oxides of nitrogen that form when fuels are burned at high temperatures, as in the engine combustion process.

Particulate matter (PM)

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 99% exhaust particulates, this pollutant is all but eliminated.


PEMS, or portable emissions measurement system, is a sophisticated mobile laboratory in a box, which is fitted to the car and analyses tailpipe emissions while the vehicle is driven on the road or a test track.


The powertrain of a motor vehicle comprises the main components that generate power and deliver it to the wheels.

Real World

Real world refers to conditions that affect a vehicle’s performance when it is being driven on the road, as opposed to being tested in a lab. Real world conditions are infinitely variable, making reliable, repeatable and comparable testing of emissions extremely difficult.

Real Driving Emissions (RDE)

RDE stands for Real Driving Emissions and refers to 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.

Road to Zero

The government has confirmed its ambition to see at least half of new cars to be ultra low emission by 2030.
The proposals are outlined in the Road to Zero Strategy, which sets out plans to enable a massive expansion of green infrastructure across the country, reduce emissions from the vehicles already on the UK’s roads, and drive the uptake of zero emission cars, vans and trucks.

See here for more details: https://www.gov.uk/government/publications/reducing-emissions-from-road-transport-road-to-zero-strategy

The automotive industry is working hard to deliver on this shared ambition, providing ever cleaner cars to suit every need. We need policies that help get the latest, cleanest vehicles on the road more quickly and support market transition for all drivers. This includes investment in infrastructure and long term incentives to make new technologies as affordable as possible.

Selective catalytic reduction (SCR)

Selective catalytic reduction (SCR) technology is one of the most cost-effective and fuel-efficient technologies available to help reduce diesel engine emissions. It injects a ureabased additive, known as Diesel Exhaust Fluid (often marketed under the tradename AdBlue®), through a special catalyst into the exhaust to convert NOx into harmless nitrogen and water.

Type Approval

Type Approval is the official process new cars must pass before they can be certified for sale. It applies to emissions and safety systems as well as the complete vehicle. All vehicles must meet the relevant regulated standards before they can be registered. The Vehicle Certification Agency is the government-appointed Type Approval Authority in the UK.

Worldwide harmonised Light vehicles Test Procedure (WLTP)

WLTP is a new lab-based test cycle which replaces NEDC. It is much more representative of real world conditions, with a wider range of temperatures, driving behaviours and speeds. It also takes into account the weight of options fitted to the vehicle and any impact on aerodynamics that they will have.