November 11, 1993

MTC Public Information Office

Metropolitan Transportation Commission

101 8th Street

Oakland, California 94607-4700

Re: 1994-2001 Draft RTIP


On page B-20 you claim that, merely by retiming traffic signals on Bay Area arterials, you will reduce CO by 17.4 tons per day, and hence comply with the Clean Air Act! This is nonsense. There isn't a shred of proof that signal synchronization reduces vehicle emissions! This can't be done by means of computer modelling, which proves nothing, but only by means of scientific research. And there is no credible scientific research demonstrating an air quality benefit from this.

I challenge you to publish the list of references on which you base your assumption of emissions reductions from signal retiming! Please send it to me by 11/19, so that I can verify it before the Commission meeting 11/24.

Waiting to hear from you,


Michael J. Vandeman, Ph.D.


February 21, 1993

Steve Coleman, Editor

Western Institute for Transportation Engineers

180 Grand Avenue, Suite 995

Oakland, CA 94612

Re: Traffic Signal Synchronization

Dear Mr. Coleman:

"Classical" traffic engineering has had as its goal the maximal throughput of vehicles, encouraging ever greater volumes and speeds of traffic. 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. Instead, traffic calming, and an emphasis on moving (or better still, not moving!) people and goods, rather than vehicles, is taking its place.

Traffic signal synchronization (TSS) is a good example of a tool that has received almost universal, and quite unjustified, allegiance. It is obviously extremely popular with motorists, but this is not a 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. But if you examine the "research", you find that there are no studies that directly measure either emissions or fuel consumption! The benefits are inferred from the smoothing of traffic. There are also several other flaws in the research. There has been no attempt to assess the effects on reverse-flow and cross-flow traffic. There has been no measurement of effects on pedestrians, bicyclists, and transit users (if "clean" transport is impeded, the effect is negative).

And there has been no quantitative consideration of the growth-inducing effects from encouraging long-distance motorized traffic at the expense of the other modes. If TSS gives people the feeling that they can travel quickly and easily, and therefore causes them to drive more, the fuel and pollution benefits can be negative.

In other words, there is absolutely no credible evidence that synchronization is beneficial to the community as a whole! Moreover, synchronizing for automobiles, and controlling signals to benefit the cleaner modes, are mutually exclusive: you can do one or the other, but not both. Another factor often overlooked is that the signals retain can their timing for only a few years, after which the same money (often, scarce "air quality" funds) must be spent again to retime them.

With so many clearly effective ways available to save energy and reduce air pollution (such as increasing fuel and parking charges), why should we waste millions of dollars on such a dubious device?


Michael J. Vandeman, Ph.D.