ON THE rare clear days in the Pacific north-west, snow-capped Mount Hood presents a spectacular sight to motorists traversing the Columbia river on the I-5. If they are driving in rush hour, they will have plenty of time to enjoy the view.

The mile-long bridge, which links Portland, Oregon with Vancouver in Washington state, is congested for four to six hours a day. Accidents that block one of the two three-lane carriageways can lead to epic traffic jams. Daily bridge lifts for maritime traffic block cars for up to 20 minutes. The I-5 runs the length of the western United States; this bit is often maligned as the only stop sign between Canada and Mexico.

Thousands of Vancouverites commute to jobs in Portland, and the bridge lies on an important route for lorries bearing freight, much of it offloaded at nearby ports. Officials have pondered a replacement for the crossing for over a decade, and they now have a plan. The two governors are publicly in favour; federal officials seem keen; local businesses have signed up, and Barack Obama has made replacement of ageing infrastructure a signature theme. Yet the proposal may go nowhere.

Under the $3.5 billion Columbia River Crossing plan, the biggest such scheme in Oregon’s history, the two bridge structures would be replaced with a ten-lane construct, including safety shoulders. Five miles of roads and interchanges on either side of the river would be built or upgraded. Drivers would pay tolls to cross; the revenues would help repay capital borrowing. Portland’s whizzy light-rail system, which many Vancouverites drive across the river to use, would extend to their side. Construction would begin next year.

But where proponents see a crossing fit for the 21st century, Joe Cortright, a local economist, sees “the last gasp of the freeway-building mindset of the 1950s”. The projections of traffic growth on which the CRC relies are hopelessly outdated, he contends; Americans drive less these days, and when the tolls kick in, traffic may drop. (This happened with a similar scheme in Seattle.) Even a CRC-hired consultancy projects a 25-50% fall in traffic when tolling begins in 2016. Toll-avoiding vehicles could clog up the nearby I-205 crossing.

Critics also say that the financing assumptions behind the plan are too rosy. If the federal government pitches in less than expected, they fear the states could be left on the hook for billions. Liberal Portlanders worry (and have filed lawsuits) about environmental damage, conservative Vancouverites about the “crime train” carrying the feckless across the water. “There’s something for everybody, which means there’s something for everybody to hate,” says Clark Williams-Derry at the Sightline Institute, a left-leaning think-tank.

Yet the biggest hurdle may be political. Oregon has approved $450m of funding for the CRC, but the Republican-run Washington state Senate is in no rush to meet its (equal) share. Legislators dismiss warnings that the money must be in place by September 30th to secure federal funds. Some suggest they are being asked to shoulder too much of the burden. “We’ll get to find out how badly Oregon wants this project,” says Ann Rivers, a Republican senator.

Talk of a “green-tea party” uniting environmentalist and conservative critics may be premature. But foes share the belief that a better design can emerge if the current plan is ditched. What it would look like is another question. Some want to raise the bridge’s height to ensure access to upstream businesses; others are obsessed with killing light rail; others urge inaction until the effect of tolls on traffic is known. For their part, the CRC’s backers barely hide their frustration with arguments they consider weighed and rejected. Each year of delay, they say, adds $50m-70m to costs.

Not every public-works project faces the CRC’s challenges, especially the choreographic difficulties involved in a two-state scheme. But it serves as a cautionary tale for those who think America’s infrastructure gap can simply be plugged by a wodge of cash from Washington, DC.