Several cities have implemented low-emission zones (LEZs) and congestion charging zones (CCZs). Researchers from the School of Public Health of Imperial College London systematically reviewed the evidence on the effects of these air pollution and congestion reduction schemes on various physical health outcomes. Although both CCZs and LEZs restrict private vehicle use within cities, they are different in practice; CCZs ban or charge most vehicles and aim to reduce congestion, whereas LEZs aim to discourage the use of high-emission vehicles.
The researchers evaluated recent research about the effect of the implementation of a LEZ or CCZ on air pollution-related health outcomes (cardiovascular and respiratory diseases, birth outcomes, dementia, lung cancer, diabetes, and all-cause) or road traffic injuries (RTIs) using longitudinal study designs and empirical health data. Several LEZ studies identified positive effects on air pollution-related outcomes, with reductions in some cardiovascular disease subcategories found in five of six studies investigating this outcome. However, results for other health outcomes were less consistent.
Six of seven studies on the London CCZ reported reductions in total or car RTIs. However, one study reported an increase in cyclist and motorcyclist injuries, and one reported an increase in severe or fatal injuries. Studies of LEZs found consistent evidence of reductions in cardiovascular disease outcomes, although results were less consistent for other outcomes. Studies of CCZs found consistent evidence of reductions in total injuries or car-related injuries. The current evidence, therefore, suggests that schemes to restrict private vehicle use in cities could reduce cardiovascular disease events and RTIs.
Evidence on CCZs is mainly limited to London but suggests that they reduce overall RTIs. Ongoing evaluation of these interventions is necessary to understand longer-term health effects.
However, the included studies did not include data on other possible contributory factors related to the intervention, such as physical activity and road noise. Further research could usefully investigate the pathways underpinning the health effects identified here. Available studies did not consider potential inequalities in effect by sociodemographic factors and gave little consideration to potential effects on bordering areas. The researchers did not include other possible effects, including congestion, residents’ quality of life, or long-term disease development; these effects probably strengthen arguments for such schemes.