The Ultra Low Emission Zone will come into force on 8th April 2019. This will affect all vehicles that do not meet the emission standards of Euro 6 for diesel engines and Euro 4 for Petrol engines. This is NOT just for Heavy Goods Vehicles. This will have an affect all motorists.
At the moment this will only apply to the current congestion charging zone, however TFL will expand the boundary to cover the North and South Circular Roads from October 2021.