Many people think that each Interstate in America gets a unique number for the whole country. That is true within a state and within same region of the country, but nationally, some interstate numbers are reused.

Interstate 86 is both the number for the Southern Tier Expressway in New York and the I-84/I-15 connector in Idaho.

Interstate 88 is both the number for the Warren Anderson Expressway in New York and the Ronald Reagan Tollway in Illinois.

State DOT generally avoid having an interstate road overlap or cross with a similarly numbered US, state, or county highway — to avoid confusion.

Within New York there is one state highway (NY Route 90 in the Finger Lakes) that crosses the NY Thruway (I-90). There is no interchange between the two highways, and this is the only time within New York when this happens.