One study estimated that traffic congestion wasted 4.8 billion hours and 1.9 billion gallons of fuel a year for urban Americans.

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"We did a two-year traffic study to analyze exactly how every single vehicle moves through Manhattan, " she says about her decision to create the Times Square pedestrian plaza.

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David Thompson, executive director of the North Carolina Association of County Commissioners, questioned the validity of the study, saying traffic fines in the state go to support schools not county coffers.

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