§ 0 Mr. Matthew Taylor
To ask the Secretary of State for Transport (1) what powers he has to control the level or speed of road traffic on occasions when pollution levels exceed proposed air quality standards; 
(2) what studies he has carried out of the potential for reducing traffic levels in the event that (a) NO2 levels in London exceed the World Health Organisation's 24 hour NO2 health guideline and (b)3 levels in southern England exceed the World Health Organisation's 8 hour 03 health guideline; 
(3) what contingency plans he has drawn up to reduce traffic levels in the event that (a) NO2 levels in London exceed the World Health Organisation's 24 hour NO2 health guideline and (b)3 levels in Southern England exceed the World Health Organisation's 8 hour 03 health guidelines; 
(4) what consideration he has given to using his powers under section 14 of the Road Traffic Regulation Act 1984 to reduced speed limits on trunk roads to reduce emissions in the event that pollution levels exceed proposed air quality standards; and if he will make a statement. 
§ Mr. Norris
A reduction in vehicle speed has differing effects on emissions of different pollutants. Any decision to impose speed limits would have to take into account levels of the pollutants of most concern.
Studies have indicated that traffic reduction may have the positive effect of reducing nitrogen dioxide 61W concentrations during winter smog episodes. However, this may have to be balanced against possible negative effects on emissions caused by congestion if traffic reduction measures involve road closures.
The Secretary of State has powers to regulate traffic only on trunk roads and motorways; traffic regulation on local roads, which comprise the vast majority of all roads, is the responsibility of local traffic authorities.
Any traffic restrictions to reduce air pollution must be developed at a local level so that all the implications can be considered—centralised contingency plans are impracticable. However, the complexity of the issue does merit further research and the Department is currently carrying out a review of existing research on how traffic management can influence air quality, with a view to undertaking a research project of our own later this year.