April 13, 1991

Metropolitan Transportation Commission

101 8th Street

Oakland, California 94607

Re: 1990-94 TIP Air Quality Conformity Assessment


At the WPPRC meeting Friday, Commissioner Weir asserted that he believes your conformity procedure is "honest" and "scientific". I don't know what will convince him (money, apparently -- lots of it!!), if a federal judge means nothing to him. My credentials will probably be equally unconvincing to him, but they aren't to most people, so I will list them.

I have a B.A. Magna cum Laude from the University of California in mathematics. I have an M.A. in mathematics (including study in statistics) from Harvard University. And my Ph.D. from the University of California at Los Angeles is in psychology, concentrating in psychometrics. I have been a computer programmer for 29 years. In other words, I am an expert in mathematics, statistics, scientific method, measurement science (including modeling), and computer science. I probably know more about all of those subjects than anyone at MTC or consulting with MTC. So, of course, it is ludicrous for any of you to try to tell me that what you are doing is "scientific". I know more about what is scientific than all of you put together!

Chris Brittle said he has tried for 11 years to understand the MTC models. Modeling is really a very simple process, when the modeler is not trying to make it mysterious. A scientific principle is expressed in the form of a mathematical formula. Then data are substituted for the variables in the formula, allowing a result to be computed (e.g. emissions of CO, from vehicle type, speed, temperature, etc.). When the formula is in dispute, statistics must be used to determine if it does what its users want it to do. The relevant factors are reliability (giving repeatable results) and validity (measuring what it is supposed to be measuring).

In terms of predicting emissions changes due to highway expansion, both your reliability and validity are in doubt: another person applying the same model, could probably get different results; and it is highly questionable whether your results will be even close to actual emissions changes. Another scientific principle is also relevant here: Garbage In -- Garbage Out (GIGO).

How can I tell? The model has invalidated itself by arriving at two absurd conclusions listed on p.II-10-35 of the 1990-94 TIP Air Quality Conformity Assessment. The first is that for 1997, "trip generation and trip distribution would not be substantially affected by the projects in the TIP". This means that people's travel behavior is unaffected by the amount and type of road space available, which is patently false. It is obvious, for example, that northern and eastern Contra Costa County would be very different, if Highways 4, 24, 242, 580, & 680 had never been built! Another example is the loss of the Cypress freeway section: this reduction in road availability eliminated, according to Caltrans, 90,000 vehicle trips per day! Some of those people apparently decided not to travel so much; most apparently switched permanently to public transit.

The second absurd conclusion is that "given local land use policy constraints, the land use allocations would not be significantly different". This, for the very same reason, is patently false. If that were true, developers would not be so eager to build new freeways (e.g. the toll road) and expand all the existing ones. The (perceived) availability of speedy freeway access to jobs, shopping, and recreation is a big factor (just as water is) in making new development viable.

I would like to propose a much simpler, and probably just as valid model: traffic expands to fill the available road space. This model has recently received a great deal of empirical support in "A Study of Freeway Capacity Increases in the San Francisco Bay Area and Greater Sacramento", by Tom Addison of EPA Region IX in San Francisco. He found that Caltrans's traffic and emissions projections were grossly underestimated.


Michael J. Vandeman, Ph.D.