To alleviate traffic congestion in Central London, the Mayor introduced the Congestion Charging Scheme (CCS) in February 2003.

The great smog disasters of the past have made clear that air pollution can kill people in a matter of days: extremely high concentrations of air pollution building up under conditions of low wind speed and stable atmospheric conditions have been associated with excess deaths in the Meuse Valley, Belgium (1930); Donora, PA, United States (1948); and London, United Kingdom (1952).