The U.S. is thawing out this week from back-to-back storms that covered large areas of the country. Airports were forced to close for periods of time, railroads were slowed or stopped and the nation’s trucking fleet was sidelined for various lengths of time in different areas.
While the storms slowed the movement of goods and people, they could not stop movement entirely. In part, this is due to the work of those dedicated to keep the roads clear and those who drive the trucks that move about 70% of the nation’s goods. It was also due in part to the system of roads that has been built over the past nearly 100 years.
The U.S. highway system is a network of interconnected state, U.S. and interstate highways. Each of the states and the District of Columbia (as well as Puerto Rico, American Samoa, Guam and the U.S. Virgin Islands) own and maintain parts of this system of roadways, including U.S. and interstate highways, which, despite their designation, are not owned or maintained at the federal level.
This series of articles will focus on America’s highways and the interstates (known officially as the Dwight D. Eisenhower National System of Interstate and Defense Highways) that collectively comprise the National Highway System, or NHS.
National Highway System
Most of us that drive on the highways and interstates are not even aware that there is an official National Highway System. It was so designated by legislation passed by the U.S. Congress and signed into law by President Clinton on November 28, 1995. The Act designated almost 161,000 miles of roads, including the Interstate Highway System, as the NHS.
According to the Federal Highway Administration, the NHS includes “roads important to the United States’ economy, defense, and mobility…” A network of strategic highways, the NHS includes the nation’s interstate highways and other roads that serve major airports, ports, rail or truck terminals, railway stations, pipeline terminals and other “strategic transport facilities.” The NHS is the largest highway system in the world.
The NHS comprises only 4% of the total road miles in the U.S. However, on its roads/highways travel more than 40% of all highway traffic, 75% of heavy truck traffic and 90% of tourist traffic travel. All U.S. urban areas with a population of over 50,000 and about 90% of the country’s population live within five (5) miles of the NHS.
And although the U.S. interstate highway system is included in the NHS, it also retains its separate identity within the NHS. In addition to the interstates, other parts of the NHS include:
The Strategic Highway Network (STRAHNET) is made up of the highways that are important to the U.S. strategic defense policy and “provide defense access, continuity and emergency capabilities for defense purposes.”
Major Strategic Highway Network Connectors are those highways that provide access between major military installations and STRAHNET routes.
Intermodal Connectors are those roads that provide access between major intermodal facilities and the other four subsystems that are part of the NHS.
The Interstate Highway System
When the new interstate system was being designed in the 1950s, the numbering grid was set intentionally opposite from the numbering system used for the U.S. routes and highways that already existed. So interstate highway numbers increase from west-to-east and south-to-north. This was done to keep identically numbered routes separated by geography in order to keep them from being confused with one another. Interestingly, there is no Interstate 50 or Interstate 60, which would have potentially conflicted with US 50 and US 60.
Therefore, interstates are numbered in this way – east-west interstate highways are even-numbered and are numbered from lowest along the Mexican border and the Gulf of Mexico and higher at the Canadian border. Interstates that run north-south are odd-numbered and the lowest numbered routes are along the Pacific Ocean and the highest along the Atlantic Ocean.
The original layout numbered interstates that ran north-south with a “5” at the end, and the east-west routes ended with a “0.” But many “fill-in” interstates have been built as well, such as Interstate 22 and I-4 (which is designated as an interstate and was built to interstate standards, but is wholly within the state of Florida). In addition, the term “interstate” has been shortened for most uses to simply a capital “I” over the years. So there are I-5, I-65 and I-90, among many.
Generally, interstates that are numbered with three digits are either beltways (loops around major cities, like I-285 around Atlanta) or spurs of their parent interstates (for example, Interstate 710 is a spur in Los Angeles, and is connected to Interstate 10).
U.S. numbered highways
Like the interstate highways, the numbered highway system (with roads often called U.S. Routes or U.S. Highways) is an integrated network that was established in 1926 (although many of the routes pre-date that year). While they are sometimes termed federal highways, their designation and numbering were coordinated among the states. In addition, these roads were built and have always been maintained by state or local governments.
U.S. numbered highways were the “original” interstate highways. Like the interstate system, most U.S. highways that run east-west are even-numbered and north-south routes are odd-numbered. However, as explained above, the numbering of the highways is the reverse of the interstate system. Therefore, routes running along the Canadian border have the lowest numbers, and the national highways along the Atlantic Ocean have the lowest numbers. Major north-south routes have numbers ending in “1” or “5,” while major east-west routes have numbers ending in “0.” However, some of the most famous routes are numbered differently (like Route 66).
Coordination of the route numbers and locations is done by the American Association of State Highway and Transportation Officials (AASHTO). The federal involvement in AASHTO is minimal; there is a nonvoting seat for the U.S. Department of Transportation in the organization. AASHTO guidelines prohibit interstates and U.S. Routes from sharing a number within the same state. However, as with other guidelines, exceptions exist across the U.S.
The various three-digit highways (also known as “child routes”) are highways that branch off or are spurs of their main one- or two-digit “parent” roadways. For example, U.S. Route 264 (signed as US 264 – without the periods) is a spur off US 64. However, US 101 is not a “child” of US 1. It is considered a “mainline” U.S. highway. That makes sense; US 1 runs from Florida to Canada along the East Coast, and US 101 runs along the West Coast. That would be a long-lost child!
When the numbers were originally assigned to the spurs or branches of numbered routes the first digit increased from north to south and east to west along the primary route. For example, US 60’s spurs ran east-west and were designated as US 160 in Missouri, US 260 in Oklahoma, US 360 in Texas, and US 460 and US 560 in New Mexico. However, similarly to the primary two-digit routes, three-digit routes have been added, removed, extended and shortened; the “parent-child” relationship is not always present or easily interpreted.
Some divided routes (such as US 19E and US 19W) exist to provide two alignments for one route. Special routes, which are most often labeled as alternate, bypass or business routes, depending on their intended use, provide a parallel routing to the main U.S. Highway.
The U.S. Highway System was the primary system of highways for 30+ years, and continued to be expanded until 1956. That was when the plan for the Interstate Highway System was designed and construction on its first highways began. As construction of various stretches of the interstate system was completed, some U.S. Routes were replaced by interstates for through traffic. However, even with the interstate system in place, U.S. highways are still key regional connections, and new U.S. Routes are still being added to the system.
Many U.S. Routes were established using the main streets of the cities and towns that they went through. This was done in part to utilize existing roads, as well as to promote commerce along their routes. In the busiest areas, bypasses or truck routes were built later to divert some traffic.
Unlike the interstate system, U.S. Routes do not have a minimum design standard and most were not built (or rebuilt) to interstate standards. However, stretches of U.S. Routes do meet those standards and are appreciated by both truck and auto drivers. New parts of the system must “substantially meet the current AASHTO design standards.”
The majority of U.S. Routes are not toll roads. The exception, for the most part, are toll bridges and tunnels; their upkeep is much higher than a normal road. AASHTO policy states that a toll road may only be included in the U.S. Numbered Highway System as a “special route,” and that “a toll-free routing between the same termini shall continue to be retained and marked as a part of the U.S. Numbered System.” At this time, U.S. Routes use parts of five toll roads
The interstate highways offer the highest speeds, widest and most number of lanes and (generally) the best driving conditions. However, it is the old national highways that often offer the best scenery and allow drivers to be closest to the cities and towns of the nation.
The next level of highways are state highways. Each state (and territory) has a system to number highways, and some are more organized than others. In addition, each state has its own highway marker design. While the number of the highway in a circle is the default, many choose a different design, such as an outline of the state with the number inside. Also, a number of states operate a system of county highways.