Internal workings of the interstate highway system
(WYTV) – Uncover the secrets of the interstate highway system.
The official name of these routes is the Dwight D. Eisenhower National System of Interstate and Defense Highways.
It started in 1956 and ended in 1992.
It covers 46,000 miles and is a quick way to get from here to there.
The numbering system is easy to understand. Even highways, such as I-80, extend east and west; odd-numbered highways, like I-79, move traffic north and south.
For east-west highways, the lowest figures are in the south and the highest figures in the north. I-10 is in Jacksonville, Florida and I-90 is in Cleveland.
For highways north to south, the lower numbers are in the west, such as I-5 in California. Higher numbers are found in the east, such as I-79 in Mercer, PA.
What about those triple-digit freeways, like the I-680? This first number, the even number 6 in this case, means that it is a ring road or a loop around a city. If the first digit is an odd number, like I-376 in Mercer County, then it’s a long connector.
Alaska, Hawaii, and Puerto Rico all have freeways, although they are clearly not connected to other states. They have special lettering – Alaska has A1 to A4, Hawaii has H1 to H3, and Puerto Rico has PR1 and PR2.
The I-90 is the longest highway in the United States, stretching from Boston to Seattle and covering nearly 3,100 miles and 13 states.
A shorter freeway, the I-95, covers only 1,900 miles but crosses the most states – 15. If you’re careful, the odd “95” tells you it’s north and south, and the high number means it’s east. I-95 connects Miami to Maine.