Courtesy of Mental Floss:

“Why Does Hawaii Have Interstate Highways?

While we’d like to believe Hawaii’s Interstate system exists for the sole purpose of annoying George Carlin, the name is actually a misnomer. Not all Interstates physically go from one state to another; the name merely implies that the roads receive federal funding. The three Hawaii Interstates (H1, H2 and H3) became Interstates as part of the Dwight D. Eisenhower System of Interstate and National Defense Highways to protect the US from a Soviet invasion by making it easier to get supplies from one military base to another.”

When a friend told me last year about the Eisenhower Interstate dealie, I was fascinated. He explained that the routes had minimum width and straightaway requirements, as well as standard markings clearly visible from the air so that they could be used as runways if needed. Though I could find no solid evidence of this in the few sites I flipped through, it’s still an interesting point to ponder.

What I did find, however, was this: “One potential civil defense use of the Interstate highway system is for the emergency evacuation of cities in the event of a potential nuclear war. Although this use has never happened, the Interstate highway system has been used to facilitate evacuations in the face of hurricanes and other natural disasters. An option for maximizing throughput is to reverse the flow of traffic on one side so that all lanes become outbound lanes.” (via Wikipedia).