For a seat-of-the-pants introduction to America's highway misery, try rattling down the joint-jangling Southwest Freeway in the shadow of the Washington Monument. On this long-neglected strip of pavement, a washboard ripple effect experts call rutting jiggles the front wheels into a dervish dance. Farther along in a newly rebuilt section, potholes already lurk, like so many blacktop booby traps.
America's road system is a marvel and a mess. With 3.9 million miles of highways and roads, many of them built in the asphalt rush of the 1950s, it is by far the world's biggest system. Ninety percent of all U.S. travel...