Yes, it’s Motordom #Fail here at Price Tags.  This time Sightline Institute researcher Clark Williams-Derry (whose must-read series “Dude, Where are my cars? is here) ruminates on our particular version of the Traffic Delusion:

It must be a syndrome. A mass delusion of endless traffic growth. Or maybe the idée fixe that the future will resemble the 1950s.

Earlier in the week I mentioned that, despite years of declines on the Tacoma Narrows Bridge, Washington’s transportation revenue forecasts assume that traffic will soon start growing, quickly and inexorably. It might be funny if the fiscal stakes weren’t so dire.

Apparently, the same mentality apparently holds sway north of the 49th parallel. Consider the newly twinned Port Mann Bridge—a project of British Columbia’s provincial government that opened to traffic last fall. The province was anticipating a rapid increase in traffic volumes to pay for construction. And while it’s too early to tell how the added road capacity will affect traffic volumes over the long haul, the declines in traffic volumes in recent years could make it very hard for the bridge to meet its toll revenue forecasts…

Port Mann Bridge - actuals vs. forecasts

(Forecasts hereactuals here.)

As with the Tacoma Narrows Bridge, the traffic forecasts actually got wackier over time. Despite roughly a decade of flat or declining traffic, the province’s transportation planners in 2011 predicted that traffic volumes would quickly catch up with where they “should” have been. In essence, the planners interpreted the slight decline in traffic between 2006 and 2011 as evidence that traffic would skyrocket even faster from 2013 through 2021.

It shouldn’t be too hard on the poor traffic forecasters. As Yogi Berra (or was it Niels Bohr?) allegedly said, “It’s hard to make predictions, especially about the future.” And that advice applies to me as well as to traffic planners—so I want to make it clear that I’m not actually predicting that real-world traffic won’t live up to the official forecasts.

Still, it’s increasingly clear that official traffic forecasts have become untethered from reality. At best, they’re based on outdated transportation models or “best practices” forged in the years when traffic volumes really were growing quickly. At their worst, they’re the result of coordinated deception to build support for politically favored projects. 

The fiscal consequences of failed transportation forecasts can be pretty dire: see, e.g., the $35 to $45 million annual hole that the Golden Ears Bridge is blowing through the lower mainland’s transportation budget, because toll revenues from the bridge aren’t keeping pace with projections, even as bond payments to pay for construction keep coming due.

But has the province actually learned anything from the Golden Ears shortfalls, or the flat-lining of gasoline consumption in the lower mainland, or the failure of its early Port Mann forecasts to line up with forecasts? Apparently not. In fact, they’re doubling down on their risky bet on traffic growth, by moving forward with a costly and aggressive plan to replace the 4-lane George Massey Tunnel with a 10lane bridge.

No doubt, the province will predict that rapid traffic growth will help pay for the construction costs for the new bridge. Which could set the province’s taxpayers for quite a shock down the road: they could easily wind up paying for yet another highway project that was supposed to pay for itself.


More on Sightline (and your chance to contribute to its work) here.


  1. While we’re using cliches as argument, how about “past performance is not necessarily indicative of future results,” and “one year does not make a trend.” Cordinated deception? Ah yes, when all else fails reason, it’s a conspiracy.

    1. it’s true that past performance is not indicative of future results, but if you’re going to make a forecast of increasing traffic, it should probably be based somehow on facts. There is nothing to support the idea that traffic is going to bounce back that rapidly – and certainly, if TransLink looks at its own performance on the Golden Ears Bridge, it would see that traffic forecasts there have been equally poor at predicting actual results.

      In many ways, these projects are based on the hope that past performance would predict the future. They basically follow the assumption that car traffic has always increased and always will.

  2. Until the options of non-tolled bridges are removed, the toll bridges will suffer. Care to show a graph that overlays the Alex Fraser and Patullo stats over these?

  3. It sounds to me like people are driving less and more fuel efficient cars ( I think proven fact in USA I also think some alternative roads to Tacoma bridge) is not golden years bridge some crazy private deal signed by Gordon Campbell We don’t need private partner ships for bridges we pay lots of taxes! Port Mann needs to lower prices and increase use City of New Westminster should toll Mcbride and Royal (maybe) Mr Price you sit high on Burnaby mountain with you tax payer subsidized job! There are people out there working Delivering and going to work visit family etc that want to get places quickly! How about if you try to find some more tax money and fix the leaky pipes and mould at SFU!

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