Impacts of roundabouts on urban air quality: A case study of Keene, New Hampshire, USA

This study seeks to understand how local air quality may have changed in the time since converting to roundabouts. A before-and-after comparison was performed using data gathered by the New Hampshire Department of Environmental Services from 1999–2014. In the time period following roundabout conversion, ozone levels stayed the same but PM2.5 levels were as much as 40% lower. As a related result, the proportion of the year that was classified as “Unhealthy for Sensitive Groups” or “Unhealthy” was 0.3–1.8% lower in the “after” time period as well. Installing roundabouts at both of its signalized intersections prone to traffic delays appears to have generated air quality benefits for Keene. While PM2.5 levels were lower in adjacent neighborhoods, this benefit may be more pronounced in a place like Keene with a similar geographic setting in terms of development patterns, transport network and topographic conditions. As planners and policy-makers propose roundabouts to relieve congestion and improve safety, this research provides additional evidence that the benefits of doing so can extend beyond the immediate intersection in certain communities; particularly when a community simultaneously installs roundabouts at all of its failing signalized intersections.
Source: Journal of Transport and Health - Category: Occupational Health Source Type: research