The Low Emission Zone (LEZ) will affect older, diesel-engined lorries, buses, coaches, minibuses and large vans (exceeding 1.205 tonnes unladen weight).

It will also affect other specialist vehicles that are derived from lorries and vans, including motorised horse boxes, breakdown and recovery vehicles, refuse collection vehicles, gritters, sweepers, concrete mixers, tippers, removals lorries, fire appliances, motor caravans, ambulances and large hearses (over 2.5 tonnes).

There will be a phased introduction of the LEZ from 4 February 2008 through to January 2012. Different vehicles will be affected over time and increasingly tougher emissions standards will apply.

http://www.tfl.gov.uk/roadusers/lez/vehicles/2535.aspx

For UK registered vehicles: if the vehicle was manufactured on or after the 1st of October 2006, no further action is required. If the vehicle was manufactured before the 1st of October 2006 then it may be affected by the Low Emission Zone (LEZ).