President Dwight D. Eisenhower signed legislation creating the interstate highway system in 1956. Since then, it has been “pivotal in shaping and supporting the country’s demographic, spatial, economic, and social development,” according to the study’s authors. But now it is showing its age and the strain of overuse.
Interstate highways make up 1 percent of the nation’s public roadway mileage today, but carry 25 percent of all vehicle miles traveled, including about half of all miles traveled by heavy trucks.
For example, the study points out that more than one-third of interstate highway bridges are more than 50 years old and need to be repaired or replaced; highways need technological upgrades to accommodate electric and autonomous vehicles; and the system’s infrastructure needs to be made more resilient to withstand threats from climate change.
In recent years, combined federal and state capital spending on interstate highway improvements totaled about $25 billion a year. Modernizing the country’s interstate highways will cost an additional $20 billion to $50 billion a year, the report estimates. The study’s authors recommend increasing the federal gas tax, which is the primary source of highway funding but hasn’t been increased since 1993.