The rush-hour creep between Vancouver and Portland could lead almost anyone to conclude that traffic on the I-5 bridge over the Columbia River will only get worse. Official estimates project cars per day to swell from the current 125,500 to 184,000 by year 2030.

That logic has compelled the Washington and Oregon departments of transportation to spend $140 million so far toward a $3.8 billion fix: five miles of new interchanges and a 10-lane bridge, all known as the Columbia River Crossing.

You’ve heard about it. Now listen again, because neither the price nor the traffic projections justifying it are true.

At the November installment of Portland Monthly’s Bright Lights discussion series, local economist Joe Cortright revealed the Crossing’s real cost will surpass $8.7 billion. And that’s only if the planners’ financial projections are correct, which, Cortright convincingly argued, is about as likely as Oregon’s summer solstice suddenly happening in January. Often using public records requests, Cortright discovered the Crossing’s funding is based on the kind of see-no-evil financing that triggered the US housing crash, from an eight-year “non-amoritization” period for major loans to tolling estimates based on steady increases in traffic, even when the actual car counts have been dropping for the last five years.

That’s right: dropping. Beginning with 2005’s spike in gas prices, traffic volumes over the I-5 bridge have declined by an annual rate of 0.8 percent. The need, the size, and, most sobering, the billions in expected tolling revenues to pay for the bridge are all based on a 1.3 percent annual growth rate.

As the 2011 Oregon Legislature and incoming Governor John Kitzhaber begin the hard work of slashing Oregon’s 10.5 percent unemployment rate and plugging a $3.5 billion budget hole, a battery of transportation officials, freight advocates, and construction groups will lobby hard to portray the Crossing as part of the cure. But Cort-right’s study makes a compelling case that the current approach is so deeply flawed that the only course of action is to completely start over, scrap the current one-bridge design, and re-envision the project as a series of smaller improvements that can be paid for and phased in over time. At November’s Bright Lights presentation, noted urban planner George ?Crandall presented one such scenario.

Of any elected official, Kitzhaber may be our last best hope to change the Crossing’s course. During his last tenure as governor, he created a kind of urban planning SWAT team that helped many Oregon communities reimagine highway projects as more community-building, business-supportive, wide-reaching ?investments. The Crossing might be bigger, but the possibilities are the same.

For certain, Kitzhaber and the Legislature are staring into the deep, dark void of Oregon’s financial woe. But if they imagine that proceeding with the Crossing as currently conceived will help fill it, they will be tossing dirt onto a time bomb.