lez

London Low Emission Zone

The Low Emission Zone (LEZ) was introduced in 2008 to encourage the most polluting heavy diesel vehicles driving in the Capital to become cleaner. The LEZ covers most of Greater London. To drive within it without paying a daily charge these vehicles must meet certain emissions standards that limit the amount of particulate matter (a type of pollution) coming from their exhausts.

Despite significant improvements in recent years, London's air pollution is still a concern.

So much so that on 3 January 2012, the LEZ emissions standards became more stringent. More vehicles are affected, and those that were already affected need to meet tighter emissions standards.

  http://www.tfl.gov.uk/roadusers/lez/default.aspx