When designed correctly modern roundabouts can significantly reduce the amount of pollutants released into the atmosphere from idling vehicles when compared to other intersections.  At signalized intersection locations, where actuated signals are not present, many drivers must wait up to 20 seconds or longer for the light to turn green, even during off-peak hours when no crossroad or opposing traffic is present on other approaches.  Since the entry control at modern roundabouts utilizes the "yield to left" principle, drivers spend less time idling their vehicles prior to entering the intersection. 

Gas prices in many parts of the country are on the rise, especially during peak travel times of the year.  Converting more intersections to modern roundabouts can reduce overall fuel consumption.

A Status Report published by the Insurance Institute for Highway Safety in the fall of 2005 ( Volume 40, No. 9) studied 10 intersections where roundabouts were considered as alternatives for an intersection improvement project, but ultimately the road authority determined to use traffic signals as the entry control.  During this study, researchers estimated vehicle delays and fuel consumption at the existing conventional signalized intersections, and compared them with estimates of what could have been expected if a modern roundabout were chosen as the preferred alternative at the ten intersections.

A key finding from the study indicated that combined vehicle delays at the 10 intersections would have been reduced by 62-74 percent, saving 325,000 hours (or 37.10 years) of motorist's time annually.  It was estimated that fuel consumption would have also decreased by about 235,000 gallons per year.  Assuming an average cost of $2.50 for a gallon regular gasoline, that is an annual savings of $587,500 for the ten intersections.  Since less fuel would have been consumed at modern roundabout intersections, fewer emissions would have been released into the atmosphere.