London low emission zone

The London Low Emission Zone (LEZ) is a traffic pollution charge scheme with the aim of reducing the tailpipe emissions of diesel-powered commercial vehicles in London. Only vehicles that do not conform to higher emission standards are charged, the others may enter the controlled zone free of charge. The low emission zone started operating on 4 February 2008 with phased introduction of an increasingly stricter regime until 3 January 2012. The scheme is administered by the Transport for London executive agency within the Greater London Authority.

More information on the Wikipedia page.