Interstate highway signs

Meaning of the numbers on an Interstate Highway sign

What do the numbers on an Interstate Highway sign mean? 

If you’ve ever driven on an Interstate Highway, you’ve probably noticed that they can be one, two or even three digits long. Did you know that the numbers have a meaning and can tell you a lot about the highway? What do the numbers on an Interstate Highway sign mean? Keep reading to learn more about the secret code behind the meaning of the numbers on an Interstate Highway sign and be prepared to have your mind blown. 

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Interstate Highway Sign Numbers and Their Meaning 

Interstate highway signs

The Interstate Highway numbers are by no means random, they have a meaning and can tell you a lot of information about the highway. The number of digits on the Interstate Highway sign tells you whether it connects more than one city, or if it only serves a single metropolitan city. 

  • Interstate Highways with one or two digits connect several regions. 
  • Interstate Highways with three digits serve a single city and are called auxiliary interstate highways. They also connect longer two-digit highways. The last two numbers match the parent highway.
  • Even numbered Interstate Highways travel East and West. 
  • Numbers for East and West Interstate Highways start with lower numbers in the South and as they move North, they get higher. 
  • Odd numbered Interstate Highways travel North and South. 
  • For North to South Interstate Highways, numbers begin with lower numbers in the West and get higher as you travel East. 
  • In three-digit Interstate Highway numbers, an odd number lets you know that it is a connector and intersects one time.
  • In three-digit Interstate Highway numbers, an even numbered first digit lets you know that it bypasses and loops with the parent interstate in two locations. 

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