When the bridge collapsed in Minneapolis, America mourned - as we should.

It will take months to determine the cause, but one effect was immediate: Political opportunists proposed higher gasoline taxes to fix our roads and bridges.

Yes, we have a road funding problem - because Congress has mismanaged our highway money for 25 years. Why trust them with more?

Since 1982, Congress has siphoned $101 billion (in 2007 buying power) from the Highway Trust Fund to subsidize the 2 percent of travel that uses mass transit. Even while bridges slipped closer to collapse, Congress diverted additional billions from trust funds to build bicycle paths.

There's talk of starting a "new" trust fund by raising gas taxes. That same line was used to sell the old trust fund - raided so often it now resembles a leaky bucket.

Even fuel taxes spent on highways are often squandered. Thanks to the Davis-Bacon Act and other bureaucratic red tape, projects cost billions more than they should. And too many projects are picked for political merit rather than public safety. The 2005 transportation bill allocated $315 million for Alaska's infamous Bridge to Nowhere, plus nearly $24 billion in 6,000 other congressional earmarks. Minnesota got $453 million in earmarks for 144 other projects, but none to fix the bridge that has fallen.

The American Society of Civil Engineers blames substandard roads and crumbling bridges for one-third of the 40,000 annual highway deaths. Estimates vary on the cost to bring these facilities up to par, but it's in the tens of billions. Fixing them years ago would have been cheaper - and our families would be safer - if Congress hadn't been spending the road money on other things. It wasn't supposed to be this way.

In 1956, gasoline taxes rose to fund interstate highways, but every penny of fuel taxes went into a new highway trust fund. Until 1982, the trust fund was used solely for roads and bridges. In 1982, Congress increased fuel taxes, but dictated that mass transit thereafter would get one-fifth whenever fuel taxes went up, even though transit users pay none of that tax.

In 1991 (the year after the Minnesota bridge was rated structurally deficient), Congress undercut roads again by mandating that 10 percent of surface transportation spending go to "transportation enhancements" - defined as bike paths, pedestrian trails, downtown beautifications, "encouraging safe walking" and building transportation museums. Today it remains illegal to spend this 10 percent on highways, roads or bridges.

Since 1991 these "enhancements" have gobbled $8.5 billion from the highway trust fund. The National Transportation Enhancements Clearinghouse reports half went to bicycle and walking trails. Those are nice to have, but it's not right to use highway trust dollars on them while our roads sag into disrepair.

So who wants to raise gasoline taxes rather than end this abuse? The leading advocate is the House Transportation Committee chairman, Rep. Jim Oberstar, Minnesota Democrat, who also champions the current system that siphons fuel taxes away from highways.

In 2003, Mr. Oberstar opposed an effort to put enhancement dollars back into highways, arguing: "It is not enough just to roll over the highways and roll over the bridges. It is more important to enhance the life of every community in America, and that is what the enhancements program has given us the opportunity to do." Sadly, the U.S. House agreed by a 3-to-1 margin.

Motorists have become Congress' cash cows. The Bureau of Transportation Statistics reports that only road users pay subsidies; all other travelers receive subsidies, with the biggest going to mass transit and rail passengers.

On average, transit riders pay about one-fourth of the cost of their travel. If they paid their own way, the highway trust fund wouldn't be running dry. Instead, road users are singled-out to shell out, like New York City's plan to tax drivers $8-a-day to raise billions for transit. Since 1983, motorists have had $101 billion taken from them and given to mass transit, plus billions more to bike paths. Why entrust more to a Congress that can't spend straight?

President Bush is right to say no to higher taxes. The right step toward fixing our roads and bridges is to fix our priorities.

Ernest J. Istook Jr., a former Republican member of the House of Representatives from Oklahoma, is a distinguished fellow at the Heritage Foundation. He was chairman of the House Appropriations Transportation Subcommittee.