The transportation emissions world is divided into two great categories: mobile sources (vehicles) and fixed sources (power plants) and much focus is channeled through this view of the transportation emissions universe. But what's missing from this picture is emissions generated by road vehicles at fixed locations, namely signalized street intersections. Idling internal combustion engines waste fuel and generate copious emissions, including GHGs, while sitting at red lights.

The modern roundabout has no signals, no red lights, operates in free-flow mode much of the time, and can dramatically reduce idle time and therefore GHG emissions.

The world has hundreds of thousands of signalized intersections that are good candidates for conversion to modern roundabouts, and most new intersections being build are good candidates. Already, France has built more than 30,000 modern roundabouts and Australia, more than 10,000. Extrapolating from either country by population gives a figure of about 145,000 modern roundabouts for the United States (only 2,000 have been built).

Computer modeling and field measurements have indicated the potential to reduce intersection GHGs by as much as 20–30% in many cases.

Fighting climate change with modern roundabouts represents a classic example of overlooked low-hanging fruit that is not on the radar of any agency, advocacy group or research team. The purpose of this presentation is call attention to modern roundabouts.

An additional significance is that the U.S. Federal Highway Administration says modern roundabouts reduce fatalities by more than 90%. No other GHG reduction strategy can make that claim.

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