When low emission zones such as the ULEZ or Congestion Charge are introduced there is an understandable concern that roads around the ULEZ may get busier.
The graph below taken from the six-month Transport for London assessment of the ULEZ presents air pollution measurements from four monitoring sites on the ULEZ boundary: Euston Road in Camden, Old Street in Hackney, Bondway Interchange in Lambeth and Marylebone Road in Westminster.
The graphs shows an increase in the downward trend of air pollution since the ULEZ came into effect in April 2019:
This suggests that the ULEZ has a positive impact on air pollution on boundary roads. These are still early findings, however more accurate data will be available later in 2020 when air quality models of air pollution across London are produced.