This follows the London low emission zone plan operating since 2008.[30][31] The ULEZ was expected to cause a 20% reduction in road traffic emissions and resulted in a drop of the worst polluting vehicles entering the zone each day from 35,578 in March to 26,195 in April after the charge was introduced.[32][33] A poll in April 2019 by YouGov found that 72% of Londoners supported using emissions charging to tackle both air pollution and congestion.[34]