The current emission factors for road transport have not been revised for a number of years. During this time several new exhaust emission regulations have taken effect, and at the request of the Department for Transport (DfT), TRL has revised the emission factors to reflect these changes.
The purpose of the revision is to enable emissions from road transport to be modelled more accurately through the addition of the latest vehicle emission test data from the DfT’s own emissions test programmes and other EU projects.
To ensure that all stakeholders’ views on the revised factors have been taken into account before the new factors are published, the DfT published a public consultation on its website on 4 August 2008 that was sent either electronically or in paper form to more than 400 stakeholders. The consultation ran for 12 weeks, and closed on 24 October 2008.
New emission factors
TRL prepared mathematical formulae that relate the rate of emission of a pollutant and fuel consumption to average vehicle speed. The new emission factors incorporate the latest test data on vehicles meeting the new vehicle Euro emission standards, the formulae also address published future standards. In preparing the formulae, TRL addressed concerns raised in the public consultation.
The formulae will be used to model road transport’s contribution to national and local air quality.