Transport for
To be allowed into the zone these trucks had to meet the Euro 3 level for particulate matter when they were registered. However they still need to pass a VOSA smoke test in order to gain a Low Emission Certificate which proves their compliance.
They will also not be allowed into the LEZ – which covers all the London Boroughs – when the limits are tightened in 2012. The 57-page document can be found at http://www.tfl.gov.uk/assets/downloads/roadusers/lez/LEZ/LEC_Eligible_Engine_List_v1.00_17_July_2007.pdf