The ULEZ expansion will come into force on 29 August 2023. When it does, it will apply to an additional five million Londoners. It will operate all day every day, charging non-compliant vehicles £12.50 daily for driving in the zone. Transport for London’s data shows that, on average, nine in ten cars driving in outer London on any given day are already compliant. Therefore, most drivers will not be charged. This briefing explains the reasons for expanding London’s Ultra Low Emission Zone, from the perspectives of environment, health, equality and the economy.