Overbuilt: Book Talk and Conversation with Erick Guerra

On November 10, 2025, Penn Institute for Urban Research alongside the Weitzman School’s Department of City & Regional Planning co-hosted a book talk and conversation with Penn IUR Faculty Fellow Erick Guerra, Professor of City and Regional Planning and Associate Dean for Research at the Weitzman School, and author of Overbuilt: The High Costs and Low Rewards of US Highway Construction (Island Press, 2025). The talk explored how decades of policy and flawed evaluation metrics have led to an overbuilding of high-capacity US highways, prompting an urgent need to shift transportation planning toward a new paradigm of accessibility over mere mobility.

The Central Argument of Overbuilt

Guerra explained that the book, whose origins trace back to discussions with students in his "Introduction to Transportation Planning" class, fundamentally challenges the ongoing policy of building and widening highways. He argued that the US highway and arterial system is overbuilt, meaning that the social, economic, and environmental costs now outweigh the benefits of adding further capacity. The goal, he emphasized, should be to find an optimum point, where investments cease and simply shuffle the distribution of things.

The Costs of Overbuilding

Guerra cited multiple forms of evidence to support the claim of overbuilding. Economically, expected benefits such as travel time savings are often nullified by construction, maintenance, land costs, and the external costs associated with the additional driving induced. Socially, the system has created pervasive car dependence, making a car a prerequisite for participation in society. Notably, Guerra highlighted, “Even though owning and operating a car is onerous for poor families, there are so few alternatives that car ownership is close to a necessity for most of the country.”

Furthermore, despite a stated focus on safety, the US has a poor traffic safety record compared to other countries. “Americans are less safe because they drive more and because they drive more under less safe conditions,” he said. “And these less safe conditions are substantially more prevalent in the places that have grown much more around highway systems.”

The Policy Trajectory and Flawed Metrics

The conversation touched on the ISTEA (Intermodal Surface Transportation Efficiency Act), a bipartisan landmark under President Bush. While it heralded a large shift in transportation priorities and the culmination of decades of reforms to respect communities previously harmed during highway-building, Guerra argued that ISTEA ultimately failed to change the fundamental direction of highway policy, acting as a continuation of past policies, and mainly emphasized using gas tax revenue to widen and rebuild roads.

Continued overbuilding persists, he contended, because finance and evaluation measures are flawed. These measures rely on congestion management through capacity increases and prediction models that use origin-destination patterns to predict future growth, ultimately concluding that chaos would ensue without new construction. The result is that “congestion remains endemic,” proving that capacity increases alone do not solve the problem.

Reversing Course and Global Takeaways

To reverse this course, Guerra proposed applying “the first law of holes," which states, “When you find yourself in a hole, stop digging.” Policy must acknowledge that the system is overbuilt and treat expansion as a last resort policy. Crucially, this involves fixing finances by decoupling highway funding from the amount of driving and ceasing to subsidize the most environmentally costly trips. Most importantly, it requires fixing what gets measured: shifting the focus from mobility (the ease of travel) to accessibility (how transportation investments affect people's ability to reach destinations), acknowledging that highways often just shuffle jobs and economic activity rather than creating new value.

Looking globally, Guerra noted that most people live in settlements similar to those found in Mexican cities, which exhibit distinct urban forms and a higher mix of modes. In these contexts, there are more opportunities to influence urban form and behaviors with transportation investments. The key takeaways in the Mexican context include investing more public dollars in transit than in roadways, focusing on financial reforms (such as charging more for more expensive trips), and prioritizing the measurement of accessibility impacts over mobility impacts.

To read an excerpt of Overbuilt, visit https://www.design.upenn.edu/post/excerpt-erick-guerra-our-overbuilt-highway-system.

About the book:

Of the approximately inflation-adjusted $2.5 trillion spent on highways from the Highway Trust Fund since its inception in 1956, about 60 percent has been spent since completing the last bit of the originally planned Interstate System in 1992. About 75 percent has been spent since the system was supposed to have been completed in 1969. State and local governments have spent trillions more on capital road investments and repairs over the same period.

Though fewer homes and businesses are destroyed, highway planners have added 75% more lane miles of urban interstate and 55 percent more secondary highways and arterials today than there were in 1992. Few Americans have a sense of how much the government spends on roadways or how, why, or where roads get built. The better informed generally understand that the federal government and states raise dedicated transportation funds through a gas tax. And these funds are primarily spent to build, widen, upgrade, and maintain major highways and arterials.

Review Quotes

"No matter how much you think you know about the unfortunate legacy of America’s interstate system, and the many ways that highways have mutilated, divided, and compromised our cities, you’ll find new insights in Erick Guerra’s Overbuilt. This concise book demolishes the false arguments that policymakers and politicians have used for decades to prioritize highway construction over everything else we value."
-Inga Saffron, Pulitzer Prize-winning Architecture Critic, 'Philadelphia Inquirer'

"The fact that we overbuilt our highway system in many parts of the country might not be all that surprising. But how and why we ended up in this situation? Those stories are worth telling, especially if we want to stop making the same mistakes time and time again. I'm thrilled that Erick Guerra did so—and did so so well. I honestly had to find another highlighter while reading this book because my first one ran out."
-Wes Marshall, Author of 'Killed by a Traffic Engineer: Shattering the Delusion that Science Underlies Our Transportation System'

"An eye-opening exploration of how outdated funding policies and evaluation measures have created an interstate system in the United States that was designed to expand, not evolve. Guerra challenges us to rethink the criteria that determine what gets built, advocating for a slow-yet-necessary process of "unbuilding" to make safer, smarter, more responsible choices for the future."
-Leslie S. Richards, Professor of Practice, Department of City and Regional Planning, Weitzman School of Design, University of Pennsylvania