Road and highway networks have reshaped much of the U.S. over the last century, linking rural towns to booming metros and expanding access to jobs and services. But the fiscal, environmental, and social cost has been steep. Americans now drive 4,000 to 6,000 more miles a year on average than peer nations, contributing to pollution, greenhouse gases, infrastructure wear, and fatalities.

That cost is evident in cities like Philadelphia and the greater surrounding area, where millions sit in traffic on I-95. Urban sprawl in the region has consumed neighborhoods, and entire communities have been divided by roads that rarely deliver fluid travel.

“The problem is we’ve built too many highways,” says Erick Guerra, professor of city and regional planning at Penn’s Weitzman School and the Penn Institute for Urban Research. In his new book, “Overbuilt: The High Costs and Low Rewards of US Highway Construction,” he shows how the national roadway network ballooned beyond its usefulness—and why adding lanes hasn’t eased congestion or improved safety.  Read more about this work and Guerra's new book within Penn Today.