Why do so many of the California Interstate Highways have the number “80” in them?
With the interstate highways, the one and two digit numbers are used for the main highways that actually go across the country. The three digit numbers designate local spurs off of the main interstate. I-80 is the major highway that goes from San Francisco to New York City. I-880, etc. are spurs off of I-80 that carry traffic to different parts of various metropolitan areas through which I-80 passes.
