Highway Numbers Aren’t Names. They’re Coordinates.

Summary by Krater

This video explores the numbering and routing system of the United States Interstate Highway System, detailing how major, medium, and minor routes are numbered and explaining the various historical and geographical exceptions.

From the video

Answers: How does the numbering system of the United States Interstate Highway System work?

• Interstate Highway System
• Highway numbering convention
• Interstate majors and minors
• Intrastate interstates
• Highway spurs and bypasses

What it concludes

• Interstate numbers follow a pattern where lower numbers are further south and west, higher numbers are further north and east, even numbers run east-west, and odd numbers run north-south.
• Interstate minors with an even first digit eventually connect back to their parent major, while those with an odd first digit (spurs) do not.
• Interstate 99 was picked out of order by Congress, defying the standard numbering pattern.
• Many exceptions exist in the interstate system due to historical routing, bypassed routes, and local naming conventions.