The sudden collapse of a 58‐​year‐​old bridge across the Skagit River in Washington state has led to renewed calls to spend more money on American infrastructure. But if that spending comes out of tax dollars rather than user fees and is dedicated to replacing bridges, it will be seriously misplaced.


The usual media hysteria followed the collapse. “Thousands of bridges around the U.S. may be one freak accident or mistake away from collapse,” screamed CBS News. “If just one of [New York’s Tappan Zee Bridge’s] structural elements gives way, the whole bridge could fall and send” hundreds of cars “tumbling into the Hudson River,” warned Business Week.


About 18,000 highway bridges (less than 3 percent of the total) built in the 1950s and early 1960s have what is now considered to be a design flaw that makes them “fracture critical.” This means that at least one major element does not have redundent support, so if that element gives way, the entire bridge could collapse. The Skagit River Bridge failed when an oversized truck that should not have been on the bridge hit a cross beam that lacked redundent support. “This does not mean the bridge is inherently unsafe, only that there is a lack of redundancy in its design,” says the American Association of State Highway and Transportation Officials (AASHTO).


To listen to the hype, you would think that bridges are failing on almost a daily basis. But put this into perspective: In 2012, more than 34,000 people died in traffic accidents. Virtually none of them died due to a fracture‐​critical bridge failure. We can do lots of things to make highways safer and reduce that 34,000. A crash program to replace thousands of bridges isn’t one of them and is likely to divert funds away from programs that are far more important.


Many of the stories about America’s infrastructure focus on the number of “structurally deficient” bridges, which (says AASHTO) doesn’t mean the bridges are unsafe but only that they require “significant maintenance and repair to remain in service.” What the stories rarely mention is that in the last two decades the number of structurally deficient bridges has declined by 44 percent, from more than 118,000 in 1992 to fewer than 67,000 in 2012, even as the total number of highway bridges increased from 572,000 to 607,000. The number of fracture‐​critical bridges has declined from 22,000 in the last four years alone. In other words, the problem is going away without the help of a giant new federal program.


Highway user fees, including federal and state gas taxes and tolls, fund nearly all construction and maintenance of state highways and bridges. The Skagit River Bridge notwithstanding, these roads and bridges tend to be in better shape than those that are locally owned, which need about $30 billion a year from property, sales, or other local taxes. User fees work better than taxes because the fees give highway managers signals about where to spend the money.


Speaker of the House John Boehner wants to dedicate oil and gas royalties to highway infrastructure. But that’s the wrong source of money and it will almost certainly be spent in the wrong places as as much if not most spending will be on glitzy projects that glorify the elected officials who appropriate the money rather than where it is really needed. For example, one sector hungry for more “infrastructure spending” is the rail transit industry, which since 1982 has automatically received a large share of all new transportation dollars. Yet rail transit does virtually nothing to relieve congestion or make our highways safer. Moreover, transit suffers from its own infrastructure crisis, mainly because it is funded mostly out of tax dollars that get spent on glamorous new rail lines rather than user fees that would be spent on maintenance.


Recent highway safety data reveal a striking 20 percent decline in fatalities between 2007 and 2010. This decline was associated with a mere 2.2 percent decline in driving, suggesting that–in the absence of the recession–a 2.2 percent increase in highway capacity and other congestion relief could have produced a similar decline in fatalities. Of the 41,259 fatalities in 2007, 13 were due to a bridge failure; there have been virtually none since then.


In short, the key to sound infrastructure is funding that infrastructure out of user fees rather than tax dollars. Since that’s true, one way to improve highway safety would be to develop a new system of user fees that local governments can tap into so that local as well as state highway engineers receive sufficient funds and the appropriate signals about where to spend money.