[2] The Interstate Highway System is a federally funded and administered but state-maintained system of freeways that forms the transportation backbone of the United States, with millions of Americans relying on it for commutes, long-distance travel, and freight transport daily, among other things.
Interstate highways are all constructed to precise standards, designed to maximize high-speed travel safety and efficiency.
Currently, five states—Delaware, Iowa, Kentucky, Mississippi, and New Jersey—use the circular shield for road signage on their state highways.
Some states may include a secondary highway system to supplement the main one, usually for a specific purpose.
For example, Texas established a system of farm-to-market roads to specifically improve access to rural areas.
Nebraska has Connecting Link, Spur, and Recreation Highways to provide access to small towns and state parks.
The Missouri supplemental route system was designed to provide access to most farm houses, schools, churches, cemeteries, and stores within the state.