As you can see, the National Arterial Highway System is simply a subset of the AASHTO Interstate Highway Numbering Conventions. The ‘missing’ routes’ are simply numbered into the existing highway grid. Some great route numbers return to national prominence and may be upgraded to interstate status in the future.

Certain important U.S. highways, such as Route 66 should be recommissioned. They can be cosigned with the Interstate/arterial routes and provide historical context.

An obvious advantage of this system is that the numbering system prioritizes what is often the most logical route. My engineer father pointed out to me years ago how the old Memorial Stadium in Baltimore, located as it was on 33rd street in a grid, could be exited very quickly as everyone just got on a street and headed “out.” The new Camden Yards, on the other hand, forces you to get in the ‘pack’ using a few major roads.

I have long suspected that interstate numbering system has obfuscated the relative desirability of other highways in the grid. Thus you will often have major traffic problems on I66 and 495 trying to enter Maryland around Washington, DC when the same trip could be accomplished easily by using I81, VA7, US 340 and I70 to avoid Washington altogether.

As bureaucrats continue to cry for more and bigger highways, doesn’t it make sense to try to better utilize the infrastructure we already have?
Copyright 2007, Kirchman Associates