Q&AZ: Why Is Interstate 17 Not A State Route?

Published: Thursday, November 22, 2018 - 5:05am
Updated: Wednesday, June 10, 2020 - 11:51am

Have you ever wondered why Interstate 17, which does not go beyond the state of Arizona, is called an interstate and not a state route? Brian Joseph Lesinski asked via our reporting project Q&AZ.

Believe it or not, it’s really a simple answer. First, some context: I-17 is the main artery between Phoenix and Flagstaff, from there you can connect to I-40 — a major east-west highway that runs through several states. Doug Hecox is with Federal Highway Administration.  

"So interstates, those routes which are designated with an 'I' and then a number after it, the interstates are all routes that are designed to accommodate heavy traffic: commercial, freight truck traffic, larger volumes of vehicle traffic just larger volumes of vehicle just generally more stuff and heavier stuff than all other roads in the country," Hecox said.

Hecox says other states, including Hawaii, also have interstates that don’t cross states lines or large bodies of water.