To reduce travel times, fuel consumption and carbon emissions, in 2004, UPS changed delivery routes to minimize the left-hand turns drivers made. Although this seems like a rather modest change, the results are anything but: UPS claims that per year, eliminating left turns – specifically the time drivers sit waiting to cut across traffic – saves 10 million gallons of fuel, 20,000 tons of carbon emissions and allows them to deliver 350,000 additional packages. If it works so well for UPS, should cities seek to eliminate left-hand turns at intersections too? My research suggests the answer is a …

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