A particularly thorny area of evaluation is the impact of transportation investment on induced travel and development…While many researchers believe that these [induced travel] impacts exist, it is extremely difficult to demonstrate their presence even for aggregate investments and certainly for a specific project. For this first round, we take the conservative position that these impacts are not sufficiently quantifiable for measurement at the provincial level. [Emphasis added.]
What they’re saying here is simple: induced travel is an inconvenient fact…so let’s pretend it doesn’t exist!
Expert opinion is perfectly clear on this issue: induced travel (the “If you build it, they will come” effect) is a real and widely observed phenomenon. When you construct new or wider roads in an urban area, people will find reasons to drive on them. In some ways it’s an effect that transportation planners are counting on: if people didn’t use the new roads, the money spent to build them would have been wasted, right? The question, then, isn’t whether new or wider roads get filled; it’s how quickly.
Todd Litman has reviewed the relevant literature on induced travel and generated traffic, and finds that new traffic can fill 50 to 100 percent of new urban road space within 3 years after a new road is opened. So any responsible evaluation of road construction ought to consider induced travel—at least nominally, and with rough estimates where precise ones are impossible.
But the Fraser Institute prefers another tack: since generated traffic is hard to estimate in advance, they’ve decided to ignore it entirely. This suits their purposes quite nicely, since as Todd shows, much of their evaluation is geared towards showing how lovely roads are. The fact that new roads can get clogged quite quickly with new traffic doesn’t fit the roads-are-beautiful leitmotif.
In case you’re wondering, the Fraser Institute positions itself as a “conservative” research center; and this paper claims that it takes a “conservative” approach to the question of induced traffic. But apparently, “conservative” in this case means “ignoring reality” and “wildly underestimating.” That sort of approach doesn’t seem particularly “conservative” to me—and if they’re trying to present themselves as a credible research center with smart ideas, they’ve done yourself a disservice with on this bit.
Todd has a longer critique of the Fraser Institute report here (pdf link), if you’re interested.