The Volkswagen Emissions Scandal and air quality standards

By Professor Roy Harrison

Professor Roy Harrison is a member of the UK government’s Air Quality Expert Group and has previously been Chair of its Quality of Urban Air Review Group. From as long ago as 1993, these advisory groups have consistently warned the UK government that there were likely to be problems in complying with air quality standards for particulate matter and oxides of nitrogen unless emissions from diesel vehicles were effectively addressed.

Cycle beating has created a major problem for air quality in European cities which were predicted to come into compliance with air quality standards for nitrogen dioxide by 2010 but have failed to do so.

Before a new model of road vehicle can be sold in Europe, it has to undergo a Type Approval Test to ensure that its emissions comply with standards set by the European Union. Representative vehicles are taken from the production line and run in the laboratory on a rolling road under different speed and engine load conditions in accord with a standard test cycle known as the New European Driving Cycle (NEDC). In recent years, car manufacturers have developed ways of mapping the engine management systems of their vehicles so as to generate low emissions and comply with the Type Approval Test requirements, while emitting appreciably higher levels of pollutants while in use in real-world driving. This so-called ‘cycle beating’ is legally allowable, although it can be highly detrimental to air quality. The European Commission has now announced plans for stricter test requirements including a real-world driving emissions test. 

The Volkswagen company went one step further in their approach to cycle beating.  They programmed their engines to recognise when they were going into the test procedure and reduce their pollutant emissions for the duration of the test. This involved using a so-called ‘defeat device’ which is illegal in the United States and probably also contravenes European regulations.

Researchers in the School of Geography, Earth and Environmental Sciences have recently been involved in trialling EDAR (Emissions Detection And Reporting), a new technology to monitor emissions of individual vehicles on real roads, under real conditions. The work has been funded by the Department for Transport under an innovation award. Find out more about this project