The Interstate Highway system is easy to understand, once you know its principles.
Not listed here, there are also standard nomenclatures for spurs and loops, and also there are smaller Interstates such as I-17, which connects I-10 and I-40 between Phoenix and Flagstaff. The number makes sense, since it is between I-15 and I-25. Even though it is not, in fact, inter state.
An interesting regionalism is that in the East I usually hear people pronounce “eye”-95, whereas in the West, Los Angeles and Phoenix mostly, people would write “I-10” but say “the” 10.