Sunday, October 20, 2013

Conservative traffic studies are radical, part 2

Last year I wrote an article entitled "Conservative traffic studies are radical" about the New Balance project traffic study that presumed, as usual, an increase in traffic volume of 0.5 percent per year. I pointed out that this assumption was untrue for the past ten years, using data from MassDOT. At a public meeting, I was able to confirm this data with the consultant that was hired to do the study. But he labeled the 0.5 percent per year assumption as a "conservative" one.

I believe it is disingenuous to call this a conservative estimate because the implications are radical. These kinds of predictions can be used as a weapon to justify deadly street widenings at the expense of the neighborhood. Historically, many widenings were brought about due to fear of increased traffic. Of course, we know that wider roads may induce additional traffic, so no problems were typically solved this way, and the result was usually more dangerous to pedestrians.

With this in mind, as I was reading through the Hotel Commonwealth expansion project PNF, I noticed this very interesting table and quote:

As shown in [Table 2-4], traffic at the specific stations has decreased within the given timeframe. In order to remain conservative, this study assumed a traffic volume increase of 0.5 percent per year.
I suppose that this represents progress, in a small way. In the past, I had to push for the project consultant to admit, in person, that traffic volumes were actually declining. Here, it is written in print. However, the evidence presented has not stopped them from making the strange leap to the usual assumption: "0.5 percent per year."

I find this to be a very strange definition of "conservative." Shouldn't that mean expecting an existing trend to continue? If traffic volumes are declining in recent years, then might they not continue to decline? Especially since we know that traffic volumes are largely a function of provided roadway space. Instead, it seems that traffic "experts" have redefined the term "conservative" to mean "does the exact opposite from the trend."

Well, all I can say is: they wouldn't be the first people to redefine "conservative" to mean something much more radical.

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