Inner workings of the interstate highway system


(WYTV) – Let’s discover the secrets of the interstate highway system.

The formal name for these roads is the Dwight D. Eisenhower National System of Interstate and Defense Highways.

It was started in 1956 and finished in 1992.

It covers 46,000 miles and is a way to get from here to there quickly.

The numbering system is easy to figure out. Even-numbered interstates, such as I-80, stretch east and west; odd-numbered interstates, like I-79, move traffic north and south.

For those east to west interstates, the lower numbers are in the south and the higher numbers are in the north. I-10 is in Jacksonville, Florida and I-90 is in Cleveland.

For north to south highways, lower numbers are in the west, such as I-5 in California. Higher numbers are in the east, like I-79 in Mercer, Pennsylvania.

What about those three-digit interstates, like I-680? That first digit, the even number 6 in this case, means it’s a bypass or loop around a city. If the first digit is an odd number, such as I-376 in Mercer County, then it’s a long connector.

Alaska, Hawaii and Puerto Rico all have interstates even though they clearly don’t connect to other states. They have special lettering — Alaska has A1 through A4, Hawaii has H1 through H3 and Puerto Rico has PR1 and PR2.

I-90 is the longest U.S. interstate, stretching from Boston to Seattle and covering nearly 3,100 miles and 13 states.

A shorter interstate, I-95, covers only 1,900 miles but crosses the most states — 15. If you were paying attention, the odd “95” tells you it’s north and south, and the high number means it’s in the east. I-95 runs from Miami to Maine.

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