The deadly 2007 collapse of the Interstate 35W bridge in downtown Minneapolis was an awful tragedy. But the lost bridge has remained useful for advocates of transportation funding.

For years, the I-35W disaster has served as a seemingly indispensable exhibit, routinely displayed during discussions of the dangerous deterioration in America's aging infrastructure. It's apparently crucial evidence for the case that America and Minnesota need to spend more tax dollars on transportation.

Our bridges, roads, railways, etc., may very well be in a state of decrepitude and disrepair that endangers Americans. But the I-35W bridge collapse is not clear evidence for that particular proposition.

Instead, the way that sad story is often pressed into service is evidence of a different sort of erosion in another essential foundation: It demonstrates a loosening devotion to diligent logic and truth-telling in our public debate and our journalism.

An old saying has it that the press is very accurate — except when it reports on a subject you happen to know something about. I've had something like that experience in the nearly seven years since — as the Star Tribune's politics and government news editor at the time — I supervised coverage of the National Transportation Safety Board's ruling on the cause of the I-35W bridge collapse.

The NTSB, the definitive word on these matters, found that the collapse had nothing to do with excessive age or deterioration. It was caused by an original design error made in the 1960s, when engineers installed gusset plates — steel braces that hold beams together — only half as thick as they should have been. A contributing factor was a heavy concentration of roadway construction materials on the bridge the day it fell.

Among the issues the NTSB explicitly ruled out as causes of the collapse were "corrosion damage" and "pre-existing cracking."

In short, the I-35W tragedy says something about bridge design processes, something about construction oversight, and maybe something about the need to double-check engineering calculations, even on long-standing structures. But it simply was not an example of a worn-out bridge giving way to the ravages of neglect. There may be such examples, but this isn't it.

Yet apparently the Minneapolis collapse was too spectacular to be left alone by those wanting to dramatize the potential costs of infrastructure neglect. And so, all these years, it has been brought up again and again by reporters, politicians and advocates in the context of America's cracked and corroded bridges.

I finally decided to sound an alarm a week ago, when the I-35W bridge was dragged into a crumbling-bridge exposé on CBS' "60 Minutes" — generally a source of sturdy journalism.

In the middle of a long report on worn-out infrastructure in distress, mainly bridges like Philadelphia's I-95 spans, Steve Croft reported:

"The I-95 bridges were built in the early 1960s and are now more than 50 years old — the same vintage as the I-35 bridge that collapsed in Minnesota back in 2007, killing 13 people and injuring 145 …"

Nothing further was said about the cause of the I-35W collapse, leaving any average viewer to conclude that wear and tear must have been the problem in Minneapolis, as it apparently is in Philadelphia.

Just days earlier, Minneapolis Mayor Betsy Hodges had appeared with other mayors at a Washington press event to support the coast-to-coast push for more transportation spending, federal and state.

"We here in Minnesota," Hodges said in a statement, "experienced firsthand the tragedy that can result when our infrastructure fails us. … I urge those who are negotiating in St. Paul to think long and hard about the consequences that we might face if we do not pass a strongly funded transportation bill."

Trouble is, a lack of strong funding did not cause the 1960s-era design error that led to Minnesota's firsthand experience with infrastructure tragedy.

It's true that even apart from the engineering error, the I-35 bridge's "fracture critical" design was outdated and less safe than newer bridge designs. But there are many thousands of such bridges in America, and it was the uncommon error that brought the bridge down.

In a January story headlined "Broken Bridges, Ruined Roads" about the Dayton administration's push this year for higher taxes to fund work on Minnesota's "aging transportation infrastructure in serious need of repair," the Star Tribune quoted state Transportation Commissioner Charles Zelle recalling the last time the state raised the gas tax, in 2008. "A bridge fell down in 2007, and that was pretty motivating," Zelle told the paper. "I say we shouldn't wait for a bridge to fall down."

Zelle's observation about the 2007 collapse's motivating power is perfectly true, so far as it goes. So are Hodges' remark and Croft's report. Many scores of references in recent years to the I-35W collapse in the context of lamenting worn-out infrastructure have this same quality. They don't explicitly say anything technically untrue about the collapse because they don't say anything at all about what caused it.

Yet when offered as part of discussions about that dangers of deteriorating bridges, these references could be both technically true and misleading — almost conveniently so for anyone wanting us to worry about what failing to spend more on transportation might lead to.

I'd like to believe that no one would intentionally create the wrong impression on such a matter. And in that case, no one will object to my clarifying the record.

D.J. Tice is at Doug.Tice@startribune.com.