When very heavily traveled highways such as the Capital Beltway around Washington, D.C., reach the half-century mark, repeated surface work is not enough to keep them functional. The problems go much deeper. "With the older base layers under the asphalt, the surface is not able to absorb the pounding the way it used to," said Doug Simmons, deputy highway administrator in Maryland. "It is at that 50-year age point, which is too close to [the end of its life]. It’s a good example of the challenges we’re going to be facing not only in Maryland but other places in the country." About a third of major roads in the U.S. need repair or replacement, this article notes.