in the first four years of implementation the lez in london prevented the release of tonnes of particulate matter and increasingly stringent regulations have continued to yield significant additional reductions to particulate matter levels it operates in tandem with the congestion charge adding an additional fee based on the emissions rating of the vehicle in question this is the first emission control scheme in the uk to target individual vehicles and represents an important stepping stone towards an ultralow emission zone ulez the tcharge has resulted in a reduction in the number of noncompliant vehicles in the congestion charging zone