Interstate Highway standards
Standards for Interstate Highways in the United States are defined by the American Association of State Highway and Transportation Officials (AASHTO) in the publication A Policy on Design Standards: Interstate System. For a certain highway to be considered an Interstate Highway, it must meet these construction requirements or obtain a waiver from the Federal Highway Administration.
An Interstate Highway under construction (I-196), with both directions of traffic moved to one side of the roadway
I-94 in Michigan, showing examples of non-interchange overpass signage in median, upcoming exit signage on right shoulder, a 1950s overpass with height restriction signage, newly installed cable median barrier, and parallel grooved pavement with shoulder rumble strips
An Interstate Highway bridge with an asphalt overlay
The Bobby Hopper Tunnel on I-49 in Arkansas was built with a 25 ft (7.6 m) height total clearance, leaving plenty of room for lighting and signs hanging from the ceiling and still exceeding the 16 ft (4.9 m) minimum for rural highways. Side clearances were reduced from the recommended 44.0 ft (13.4 m) to 38.0 ft (11.6 m) due to cost concerns.
Interstate Highway System
The Dwight D. Eisenhower National System of Interstate and Defense Highways, commonly known as the Interstate Highway System, or the Eisenhower Interstate System, is a network of controlled-access highways that forms part of the National Highway System in the United States. The system extends throughout the contiguous United States and has routes in Hawaii, Alaska, and Puerto Rico.
I‑55 under construction in Mississippi in May 1972
Commemorative sign introduced in 1993. The system was established during Dwight D. Eisenhower's presidency, and the five stars commemorate his rank as General of the Army during World War II.
The fervor of urban renewal led to the routing of Interstate 81 through the middle of Syracuse's 15th Ward in the 1960s. The viaduct is now slated for demolition.
I-95 in Columbia, Maryland, built to modern standards.
