Interstate Exit Numbers

The States typically use one of two methods of numbering the Interstate interchange exits.* The Consecutive numbering system — Starting at the most westerly or southerly point on each Interstate route, interchanges are numbered consecutively. Thus the first interchange becomes Interchange #1. Each succeeding interchange is numbered consecutively as #2, 3, 4,

• The Milepost numbering system — All Interstate routes are mileposted beginning at the most westerly or southerly point. The beginning point is milepost ‘0’. If the first interchange on the route is located between milepost 4.0 and 5.0, it is numbered as Interchange #4. The next interchange, if located at milepost 8.7, would be numbered as Interchange #8, etc. With this system the motorist can easily determine the location and distance to a desired interchange.