This article is the first of our “Navigating The Roadways” Series.  In this series, we explore the new world of road tripping without paper maps and right-seat navigators.  This installment – Making Sense of the U.S. Interstate Highway System.

Where would we be without highways to get around this country today? To briefly put some history into perspective, the number of registered motor vehicles was less than 500,000 in 1910 and rapidly increased to more than 26 million on the road by 1930. The time when highway transportation could be left to private entrepreneurs was quickly passing.  Today there are two hundred and fifty six million cars and trucks on the road in the United States using four million miles of roads.  Forty-six thousand miles of these roads are designated “interstate highways.”

With roots that started in the 1920’s, the Interstate Highway System of limited access highways is one of our nation’s great assets.  Actual funding and building wasn’t funded  until Congress passed the Federal-Aid Highway Act of 1956. Today, it is the largest highway system in the world and largest public works project in history.

One of the components of the National Highway System, was to improve the mobility of military troops to and from airports, seaports, rail terminals, and other military bases as a system of roads was identified as critical to the U.S. Department of Defense. The system has also been used to facilitate evacuations during natural disasters.

To say the least, determining a standardized means of naming and designing roads was not highwaygreensboro_road_signsa simple task. Initially some roads were best described as trails, some crossed states, some circle major cities, others had well established “famous” names, etc. Furthermore, the US geography did not lend itself to a perfect grid. Nonetheless, it was ultimately highway-3-digit-interstate-shielddecided to provide one and two-digit even numbered interstates to run east and west with lowest numbers in the south and highest numbers in the north. Conversely, one and two-digit odd numbered interstates run north and south, with lowest numbers in the west and highest numbers in the east.  At least that was the general plan, and not necessarily true every single time.

For bypasses, ring roads and other auxiliary interstates that help assist traffic around cities, you will find three-digit interstate numbers with the second and third digit the same as the associated highway.  Odd-numbers in the first digit mean that the road connects only at one end; even number first digits mean that the road connects at both ends.  For example, Interstate 295 is the bypass around Jacksonville, Florida, connecting Interstate 95 at each end of the city. 


The name “interstate” does not mean that the highway has to run between states.  It is true that Interstate 95 runs the length of the eastern seaboard, and Interstate 5 runs the length of the west coast north and south.  But Interstate 4 is contained entirely within the state of Florida from Daytona Beach to Tampa, and Interstate H-1 spans twenty-seven miles on Oahu.  Alaska and Puerto Rico also have designated interstate highways.

About signage:  Within the United States, road signs are generally standardized by federal regulations. The Manual on Uniform Traffic Control Devices (MUTCD) and its companion volume the Standard Highway Signs provides for standardized signage with occasional exceptions.

Regulatory signs provide instructions to motorists, pedestrians, and cyclists. Signs such as stop, no parking, no turns, and yield are considered regulatory signs. Some have special shapes, such as the 80th Birthday of the MUTCDoctagon for the stop sign and the X shape for railroad crossings. Some signs can be localized, such as no parking, and some are only found in state and local jurisdictions as they are based on state or local laws, such as New York City’s “Don’t Block the Box” signs.

Roadway signs increasingly use symbols rather than words to convey their message. Symbols provide instant communication with roadway users, overcome language barriers, and are becoming standard for traffic control devices throughout the world.

The color and shape of roadway signs is are also important indicators.  For example: Red on signs is limited to stop, yield, and prohibition signs while yellow conveys a general warning message. Likewise, the sign shape alerts roadway users to the type of information displayed on a sign. For example: Regulatory signs are octagons for stop and inverted triangles for yield while diamond-shaped signs signify warnings.

Mile markers also provide essential information during your journey. highway-mile-marker9891310893_fba6826823_z Interstates provide a type of index of small green or blue signs marking each mile (and sometimes less than a mile) of the highway. It is an ongoing odometer to tell you where you are on the highway. Miles are numbered from the west to the east, and from the south to the north, always restarting from 0 at the border of each state. So if you are traveling south or west, you know exactly how many miles it is to the state border.

highway351px-vdot_interchange_exit_direction_signBy now, most states have applied the newer federal guidelines and renumbered their exits according to the nearest mile marker as well. It this case, you can readily determine how many miles away your next exit is via some simple math of your current mile marker and exit number. And  within most states, Interstate signage configurations also help the driver best prepare for the proper lane to make an upcoming exit. For example, the exit number “tab” on top of the sign is flush left to indicate a left exit or flush right to indicate a right exit.

Note that left exits are much less common than right exits. Left exits are often also  marked in a yellow section at the bottom of exit signs.

Automated Navigation has taken over our travel planning.  There was a day when we relied on maps and even the AAA “Trip Tiks” (remember those?) to get us to our destination.  audi_mmi_navigation_plusToday we use our smart phones and dash-mounted nav systems to get us where we want to go.  We have, to some extent, lost our road orientation skills by depending on the voice telling us to “exit in two miles” and “your destination is on the left.”  A couple of weeks ago, we used Siri on an iPhone to help us find a certain restaurant for breakfast in North Carolina.  After several wrong turns and some confusing instructions, we found the restaurant – and realized that we had actually driven past it a few times while following Siri’s instructions.  Embarrassing to say the least.

Using GPS navigation doesn’t mean that you no longer have to understand the road systems or even know where you are going – in fact, it means that you have to better understand the “lay of the land” before setting out on your adventure.  Check the mapping program in your smart device – Google Maps and Apple’s mapping programs are both really good – and get an understanding for what roads go where.  The GPS is not always correct and not always offering the best/most efficient route.

Look for future articles with our Navigating the Roadways Series, including information on how to get the most out of your GPS system.


Read more about it here:

FHA Highway History

Eight Tips to Help You Navigate the Interstate Highway System

Interstate Highway System

Manual on Uniform Traffic Control Devices

United States Road Symbol Signs

Road signs in the United States

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