April 07, 2020

Truck weights revisited

I find it necessary to respond to a guest commentary that ran in your paper on Sept. 20 by Guy Bourrie. Specifically to his assertion, “A truck weighing even a legal 80,000 pounds is more than twice as likely to be involved in a fatal crash as a truck weighing about 50,000 pounds.” He indicates the source as a 1988 University of Michigan Transportation Research Institute study called “Analysis of Accident Rates of Heavy-Duty Vehicles.”

The study looked at some hypothetical situations and some practical, real-world situations. In the hypothetical situation the report indicated vehicle combinations greater than 65,000 pounds would have a fatal accident involvement rate 42 percent higher only under certain hypothetical circumstances. Real world rarely duplicates hypothetical situations.

In fact, when you look at the normalized fatality rates of the accidents studied in the report, it shows that there were two peaks in the data. One at 15,000 pounds, then the trend goes generally down and then climbs to a peak again at 65,000 pounds and then returns to declining; to the point that where vehicles weighing more than 80,000 pounds have an accident rate of approximately one-half of those weighing 65,000 pounds. I thought I was fairly well educated but I don’t understand how 42 percent equals twice as likely.

The report concluded that the road and traffic conditions had the greatest influence on the fatality rate than any of the other factors they looked at.

The one point we agree on is that the Wilbur Smith Associates study clearly indicates that it would cost the state of Maine between $3 million and $4.1 million if the current weight exemption on the Maine Turnpike is removed.

In my opinion, both reports Bourrie cites as sources would unmistakably validate that the six-axle 100,000-pound combination vehicle should be allowed on the interstate system.

Dale E. Hanington


Maine Motor Transport Association


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