This story is Part 3 of a series. To read Part 1, click here. To read Part 2, click here.
The 1919 transcontinental convoy changed freight movement in America (Part 3)
Even as the vision Dwight D. Eisenhower had of an interstate highway system took shape, planners realized that a subset of routes was needed if the highways were to reach critical areas of the nation’s commerce.
The original Eisenhower plan called for connecting major cities along transportation routes. In many cases, those routes passed directly through city centers, bisecting cities, not only disrupting commerce but also creating socioeconomic strife. To help offset these impacts, the subset of the interstate system required construction of a series of spurs, bypasses and beltways (auxiliary highways) to help travelers and shippers navigate or avoid major cities and their associated traffic.
While the major interstates — those traveling east/west or north/south across the country — were identified mostly by two-digit numbers (such as Interstate10 or Interstate 95), the auxiliary highways constructed in and around cities were given three-digit numbers (like Interstate 495, for example).
The reason for naming certain types of interstate highway by the digits that have been chosen is not random. The interstate highway system has specified guidelines for nomenclature, depending on the type of highway represented.
What’s in a name? Here’s a crash course in interstate terminology:
Spurs
Spurs are often short sections of interstate serving areas of cities that would not otherwise be accessible by a main highway. They often end at city street crossings, sometimes even at stop lights.
Spurs may also represent sections of highway planned for extension in the future but for which funding has not yet been released. Or a spur may connect two unrelated highways, such as U.S. Highway 90 and Interstate 110 in Biloxi, Mississippi.
The key to identifying a spur is that it usually comes to an abrupt end, and that end is not another interstate.
Bypasses
A bypass is typically a section of highway designed to avoid a direct interstate route through high-traffic city centers.
While they were not originally a part of the interstate highway system, as cities became clogged with traffic, bypasses were constructed to allow thru traffic to travel unimpeded around cities or metropolitan areas. Examples of bypasses include Interstate 440 south of Nashville, Tennessee, and Interstate 220 around Shreveport, Louisiana.
One of the most noted “bypasses” in the U.S. is not really a bypass at all. Interstate 635 forms a partial loop around the Dallas-Fort Worth (DFW) area — but it is not a bypass in itself. Known as the LBJ Freeway, Interstate 635 is joined at both ends by spurs, U.S. highways and Interstate 20 to form a complete loop — also known as a beltway — around DFW.
Typically, however, a bypass breaks off from the main interstate on one side of a city and rejoins it on the other side.
Beltways
A beltway, or loop, surrounds a metropolitan area and normally consists of a bypass that connects to other routes before ultimately rejoining an interstate on the opposite side of where the beltway began.
There is not normally a beginning or ending point for a beltway; one could travel around a city many times and — unless they exit onto a main interstate — the beltway continues to circle the city.
Beltways are typically preceded by an even number in the three-digit numbering scheme. Examples include Interstate 495 around Washington, D.C., Interstate 275 in Knoxville, Tennessee, and Interstate 279 in Pittsburgh.
Nomenclature
When the interstate system expanded beyond Eisenhower’s original plan, it became clear that a system of naming each route was necessary. Rather than haphazardly assigning numbers to interstates at random or as they were adopted into the system, planners decided that a geographical system would best serve travelers. Through such a system, travelers could get a general idea of where they were in the country simply by checking the numbers and determining whether they were about to turn onto a spur, bypass, or beltway.
North/South interstates
Beginning at the western side of the lower 48 states, main interstate numbers end with the number 5; the first digit increases as you move eastward across the U.S.
Consider Interstate 5, which runs up and down the west coast, and Interstate 95, which traverses the east coast. Between these interstates, you’ll find Interstate 35 running northward from Texas, Interstate 55 traveling from the Gulf Coast to the Great Lakes and Interstate 75 running from the Great Lakes to southern Florida.
East/West interstates
On the other hand, interstate routes dubbed with even numbers — 10, 20, 30, etc. — run east/west across the country.
The southernmost route is Interstate 10, along the Gulf Coast region. Interstate 40 runs nearly coast to coast through Ashville, North Carolina, to Little Rock, Arkansas, Alburquerque, New Mexico and points beyond.
And, lest we forget the roots of the U.S. interstate system: Interstate 80 — the Lincoln Highway the route of the 1919 military convoy — runs from coast to coast, from New Jersey all the way to San Francisco.
Spurs, bypasses and beltways
Current plans call for the addition of interstates between the main routes, especially running north/south across portions of the country. For this reason, interstate numbers like Interstate 49 and Interstate 69 have been set aside to identify these future routes, some of which are already being developed as spurs and bypasses.
These main two-digit interstates have become the basis for naming the spurs, bypasses and beltways surrounding or passing through cities.
Spurs are normally named with three digits, the first being an odd number (1,3,5, etc.). The remaining two numbers indicate the interstate from which the spur originates.
Bypasses, which are also named with three digits, begin with an even number (2, 4, 6, etc.). The following two numbers are the interstate that the bypass often connects to at each end. In some cases, where the route connects to two different major highways, bypasses can be treated as spurs to avoid confusion.
Finally, beltways are named with three-digit numbers; the first digit is an even number and the last two digits indicate the interstate from which the beltway originated. Again, beltways have no terminus; however, the mileage markers do have a beginning and ending point.
Continued growth
With the completion of the “original” planned interstate system completed in 1992, the routes consumed 40,000 miles of highway at a cost of $114 billion (equivalent to over $600 billion today). Since that time, other routes have been added and both mileage and cost continue to grow. Today, the entire interstate system consists of some 49,000 miles.
But all the growth did not come without consequences for Americans, and specific socioeconomic groups have been impacted. Much opposition to the interstate system boiled over in the 1960s and 1970s. In Part 4 of this series, we’ll consider the pros and cons of the interstate system and how the “haves” and “have nots” have reacted to its development.
Since retiring from a career as an outdoor recreation professional from the State of Arkansas, Kris Rutherford has worked as a freelance writer and, with his wife, owns and publishes a small Northeast Texas newspaper, The Roxton Progress. Kris has worked as a ghostwriter and editor and has authored seven books of his own. He became interested in the trucking industry as a child in the 1970s when his family traveled the interstates twice a year between their home in Maine and their native Texas. He has been a classic country music enthusiast since the age of nine when he developed a special interest in trucking songs.
