page_title: Interstate Highway standards
section_title: Exceptions
hierarchical_section_title: Interstate Highway standards / Exceptions
caption_attribution_description: English: Interstate 93/US Route 3 in Franconia Notch
context_page_description: Standards for Interstate Highways in the United States are defined by the American Association of State Highway and Transportation Officials 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.
context_section_description: The standards have been changed over the years, resulting in many older Interstates not conforming to the current standards, and yet others are not built to standards because to do so would be too costly or environmentally unsound.
  Some roads were grandfathered into the system. Most of these were toll roads that were built before the Interstate system came into existence or were under construction at the time President Dwight D. Eisenhower signed the Federal Aid Highway Act of 1956. One example is the Pennsylvania Turnpike, which originally had a very narrow median that later required the installation of a Jersey barrier due to heavy traffic loads.
  Interstate 35E through Saint Paul, Minnesota is an example of a freeway that was not grandfathered into the system that is nonetheless an exception to standards. Initially designed in the 1960s, but not opened until 1990, the freeway has a speed limit of 45 mph (72 km/h), and does not allow vehicles weighing over 9,000 pounds (4,100 kg) GVW. This is due to political opposition from surrounding homeowners in local neighborhoods, which greatly delayed and modified the project.
  Interstate 75 on the Mackinac Bridge between St. Ignace and Mackinaw City, Michigan, is undivided. The bridge was designed before the start of the Interstate Highway System, and it was grandfathered into the system.
  Interstate 93 through Franconia Notch, New Hampshire is also a notable exception, being a super two parkway with a speed limit of 45 mph (72 km/h).
  All the unsigned Interstates in Alaska and Puerto Rico are exempt from Interstate Highway standards and are instead, per Title 23, Chapter 1, Section 103 of the U.S. Code, "designed in accordance with such geometric and construction standards as are adequate for current and probable future traffic demands and the needs of the locality of the highway".
caption: Interstate 93 super two through Franconia Notch, New Hampshire
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