Claims that signal synchronization reduce emissions and save fuel have been used to promote its use in numerous cities around the world. Millions of dollars have been spent to implement it.
Traffic engineers use it to justify their employment.
And yet these claims have never been scientifically demonstrated. Recently, this goal has increasingly been questioned, since it has led to increases in noise, pollution, accidents, global warming, and, in general, a lower quality of life. It is obviously extremely popular with motorists, but this is not sufficient justification for it, particularly since we need, for environmental and social reasons, to give preference to pedestrians, bicyclists, and transit users. The usual justification given is that it allegedly reduces fuel consumption and emissions of air pollutants. The benefits are inferred from the smoothing of traffic.