Although London's CCS was implemented strictly to ease traffic flow and not necessarily reduce pollution, early projections had hinted that air quality in central London could improve because of CCS. However, HEI's study did not find consistent evidence of improved air quality resulting from the CCS, probably because air pollution respects no boundaries. Therefore, any benefit of the CCS appears to have been lost or offset by increasing regional pollution. HEI claims that any CCS-related changes in pollutant levels at roadside monitoring sites were barely even measurable.
At the time of its implementation, London's CCS was a world-leading traffic intervention program aimed at controlling excessive congestion in central London. However, the findings presented by HEI suggest that such a scheme is most successful at reducing traffic, and should be promoted as such.
[Source: Green Car Congress | Image: Cristiano Betta – C.C. License 2.0]