Across the zone, there has been a 21% reduction in the level of nitrogen dioxide which Sheffield City Council suggests is due to vehicle upgrades away from more traditional vehicles. This scheme will continue, as the urge to improve air quality remains as poor air quality can have devastating impacts on public health.
Further information, and data can be found in this article https://airqualitynews.com/local-government/a-year-on-data-reveals-the-success-of-sheffield-clean-air-zone/