Planning Your Trip - Defensive Class

Odd numbered interstates (1 to 2 digits) are north-south routes. They start with I-5 on the West Coast to I-95 on the East Coast.

3 digit numbered interstate highways connect major highways. If the first digit is an odd number this usually represents a "spur" route heading from an interstate to a destination, such as a city center. An even number means the highway connects to a interstate at both ends (typically a "beltway" or loop).