Roundabouts as a Strategy to Improve Air Quality

Modern Roundabouts, Global Warming, and Emissions Reductions: Status of Research, And Opportunities for North America (16 page pdf, Tony Redington, Canadian Transportation Research Forum, May 2001)

Also discussed here: Modern Roundabouts and the Environment (Road Commission of Washtenaw County)

And here: Air Quality and Modern Roundabouts (Wisconsin Dept Transportation, Aug, 21, 2008)

And here: Auto Roundabouts Reduce Fuel Consumption, Air Pollution 20-30%! (The Optimistic Futurist, Mar. 26, 2011)

The focus today is on how roundabouts can and are being used as a tool to reduce vehicle emissions at intersections compared to the use of traffic lights. The introduction of 100 roundabouts in Vermont was expected to reduce greenhouse gas emissions by 8%, addition to significantly fewer collisions and fatalities at intersections



Key Quotes:

“Modeling and empirical studies of busy highway intersections document a substantial short term benefit from installing modern roundabouts. Motor fuel consumption and associated air pollutants are reduced, and the primary global warming gas (GHG), CO_2, is significantly cut.”

“The US Environmental Protection Administration (EPA) Mobile 5 model (Mobile) does not contain a module that effectively models intersection performance.”

“The magnitude of impact from roundabouts on Vermont statewide motor fuel use is suggested by a hypothetical installation of roundabouts in place of signals at 100 busy intersections.. According to models, this change would decrease total annual motor fuel use by approximately 8% of 1997 statewide consumption.”

“25 roundabouts replacing existing traffic signals in the City of Burlington, Vermont would equate to over 20% of that City’s goal of bringing GHG emissions to 10% below the base line 1990 level”

“At the metropolitan level, the roundabout savings at busy intersections represents a tool to meet the Burlington goal of reducing 2005 GHGs generation by 256,000 tons. Transforming 25 signalized intersections with substantial traffic volumes would.. amount to about 61,000 tons of CO₂..based on assuming 250,000 annual reduction in fuel use per intersection average and 19.57 pounds of CO₂ per gallon of motor fuel”

“The City of Carmel, Indiana. found that when roundabouts replaced traditional intersections, accidents with injury reduced by 78%, and that cost of construction of a roundabout was $125,000 less than constructing an intersection with traffic lights”

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