June 29, 2006, will mark the 50th anniversary of the interstate highway system—a triumph of modern engineering that revolutionized the nation. By ensuring safe, fast, and inexpensive travel from city to city, this vast network of divided freeways helped to unite the nation both culturally and economically. Using the interstate highway system to move goods efficiently from ports, rail lines, and manufacturing centers to towns and cities across the nation, the United States rose in the postwar era to become an economic and political powerhouse.

On the occasion of its anniversary, it is appropriate to examine the system’s past, present, and future, and the three sections of this special report do just that. The design and construction of the first segments of the system during the 1950s and 1960s showcased the knowledge, ingenuity, expertise, and dedication of the engineers and construction professionals who literally moved mountains to accomplish their task. As construction continued into the 1970s and the decades that followed, the skill of those professionals would again be tested, this time by the need to meet environmental and community needs as they proceeded with construction and by the difficult choices that funding shortfalls made necessary. A testament to their achievement is that the vast majority of the system has stood the test of time and continues to deliver as they intended. But the sheer volume of traffic—particularly truck traffic—that the system must accommodate is exacting a toll on performance levels. New management approaches—for example, high-occupancy/toll (HOT) lanes and such advances as those embodied in intelligent transportation system (ITS) technologies—are helping to meet today’s challenges, and the future is by no means bleak. But as this report notes, strong leadership will be required to inspire—and fund—a long-term, comprehensive transportation plan that can stand as a worthy successor to the Federal-Aid Highway Act of 1956.