Get A Clue 2000 - OHDaMN Archives

This article was written with a map of the U.S. as the only source material. The rest was dredged up from some forgotten memory bank or made up on the spot. Once upon a time, I had an idea that we could use highway designations in a clue whose eventual answer would be the name of some city or state (Chicago was the intended target, with the clue site ending up at either the sports bar or pizza joint of simialr name.) Needless to say, since you never saw the clue, we never actually used the idea. The article is included in this archive largely because it is all original material, and of some nominal informative value.

The Interstate Highway System

The Interstate Highway System is a collection of high-speed multi-lane limited access highways that exist in all 50 states (including Hawaii, for some odd reason) and which greatly facilitate the movement of people and freight over both long and short distances. The first legislation that became a catalyst for Interstate Highway construction was introduced into congress and later signed into law by President Dwight D. "Ike" Eisenhower during the 1950's. While the highway designations and much of the initial planning for the Interstate Highways were provided by the federal government, construction and maintenance of the system is carried out by individual State Deepartments of Transportation, though of course they make use of federal grants and other funds to do so. Originally intended only as a means to encourage interstate commerce, they have become indespensible locally to both daily commuters and those driving into and out of our major metropolitan centers seeking shopping and entertainment that is not otherwise available in small hometowns and neighborhoods.

Interstate Highways are numbered sequentially in such a manner that by knowing the two digit designation of an Interstate Highway you can determine both its orientation and rough geographical position in the United States.

East-to-West highways are given even numbered designations. The largets and most important traffic arteries are numbered by tens, starting with I-10 (which runs from Jacksonville to Los Angeles in the south) and going up to I-90 (which runs from Boston to Seattle in the north). Any single digit even number lies south of I-10, such as I-4 in Florida or I-8 just north of the Mexican border in California and Arizona. Similarly, any highway designated with a two digit even number higher than 90 lies north of the line from Boston to Seattle, such as I-96 in Michigan or I-94, which cuts a path from Wisconsin through to Montana where it then merges with I-95.
North-to-South highways are given odd numbered designations. The largest of these highways are given numbered designations ending in a 5, starting with I-5 running parallel to the Pacific coast in the west, and ending with I-95 which similarly mirrors the Atlantic coast in the East.
Other Interstate Highways can be more or less accurately placed within this grid by interpreting the two-digit highway designation, though of course some alterations are made to accomodate natural geographical features and to encompass populated areas.

Three-digit numbered designations do not follow the system spelled out for two-digit highway names. All three-digit designated highways are relatively short and most are contained within a single state. Seldom will such a highway cross state borders. In all cases involving a three-digit highway name, the last two digits will correspond to the Interstate Highway from which the new, three-digit designated highway originates. The first digit in the highway name is what tells you whether the highway is a Spur or a Loop. Spurs, which are given an odd numbered first digit, radiate outward from a metropolitan area into areas surrounding the city, such as I-575 to the north of Atlanta. A Loop, given an even numbered first digit, will go through or around a metropolitan area before once again joining the interstate from which it branches, as does I-285 here in Atlanta.

Interstate Highways are most notable for being among the first limited access highways built in America. The term "limited access" means motorist can only get on or off the highway at select points, called exits, where ramps and extra lanes facilitate the departure of cars and the merging of new cars into existing traffic, both without significantly slowing down those motorists already using the Interstate Highway. In a few states (including Georgia at one point in time) exits are numbered sequentially, though a majority of states now follow a system where the exit number is determined by the distance in miles from the state line. In either case, the exits are numbered in order from west to east, or from south to north. In cases where highways merge, the exit numbering of one Interstate Highway will take precedence over the other. (One such example is the Downtown Connector through Atlanta, where exits for I-75/I-85 use the numbers for I-75, leading to the initially confusing circumstance on I-85 when exits numbers jump forward by more than 100 and then "run backwards" to the north of town when the original numbering system resumes.) The Georgia State legislature passed the law changing exit numbers from strict-sequential to mileage-based back in 1997, though the change did not go into effect until early 2000. (The three year delay was supposedly for driver education and public awareness of the change, but I don't rmember hearing about it, do you?)

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