All About The InterState Highway System. What’s The Longest Highway In The US?

All About The InterState Highway System. What’s The Longest Highway In The US?



In 1926, the United States Numbered Highway System was established as the first official mapping and numbering framework of America’s national roads and highways, but it was only with the Act developed in 1956 that a proper system, guided by standards and regulations, was implemented across the country.The American Association of State Highway and Transportation Officials (AASHTO) sets out various standards that interstates need to adhere to, and include the following:Controlled access is an absolute necessity; traffic lights, toll booths, and ramp meters are allowedSpeed limits: These may be determined by the individual states, but federal law provides the foundation. Typically, Northeastern and coastal states have lower speed limits while inland states have higher limits. At-grade intersections must be avoidedFederal traffic sign specifications must be complied withExceptions to these standards can only be granted by a waiver from the Federal Highway AdministrationToday, the names and numbers of roads, highways, and interstates in the US are allocated by AASHTO as developed in 1957. When it comes to the interstate numbering system, in particular, these are the guidelines (although some exceptions to the rule exist):Primary interstates get one- or two-digit numbersShorter routes, including loops, short connecting roads, and spurs, get three digits, with the last two digits matching the parent routePrimary routes running from East-West are assigned even numbers For North-South routes, odd numbers are assigned Any route number divisible by 5 is seen as a major artery that carries traffic over long distancesConcurrency, or overlap, is allowed where two routes can share the same roadway