Jeff from Aurora writes, “What's driving you crazy? Why are I-225 and I-270 officially interstates? They barely span between counties, let alone states.”
This is an interesting question, Jeff, as you could say the same thing about the interstate highways in Hawaii or Alaska.
The interstate designation really has more to do with the uniform geometric and construction standards for a particular highway more than if they connect between states. According to the American Association of State Highway and Transportation Officials (AASHTO), the original examples of design standards for the Interstate System included full control of access, design speeds of 50 to 70 miles per hour depending on type of terrain, a minimum of two travel lanes in each direction, 12-foot lane widths, 10-foot right paved shoulder, and 4-foot left paved shoulder. Initially, the design had to be adequate to meet the traffic volumes expected in 1975. Later, these requirements were changed to a more general 20-year design period to allow for evolution of the system.
I-270 and I-225 met those requirements when they were first constructed in the 1960s so they are part of the interstate system. These short interstate segments are designated as spurs or beltways that branch off a primary interstate like I-25 or I-70. Beltways are designed to help move traffic away from urban cores or around cities. They are also intended to serve metropolitan traffic moving from main highway to main highway.
That’s why they have a three-digit number designation. If the three-digit number starts with an even number, like I-225 or I-270, that means they connect to an interstate at both ends. An odd numbered interstate with three digits, like I-190 in Buffalo, meets a primary interstate at just one end. So, for our purposes, I-270 is a spur of I-70 while I-225 is a spur off I-25.
According to the US Department of Transportation, whether the interstate highway designation is multi-state or one-state, the key is that each highway must meet Interstate standards, be a logical connection to the Interstate System, connect to an existing route, or be a congressionally designated future Interstate corridor that eventually will connect on at least one end.
Although many interstate highways pass through multiple states like I-25 and I-70, many others are located in only one state like in Alaska or Hawaii. Congress authorized the Federal Highway Administration to designate interstate highways in three locations without connection to other states. Alaska has four interstates named A-1, A-2, A-3, and A-4. Hawaii also has four named H-1, H-2, H-3, and H-201. Puerto Rico has three named PRI-1, PRI-2, and PRI-3. The statute though exempted Alaska and Puerto Rico from meeting full Interstate standards.
The interstate highway system was basically conceived in 1939 but wasn’t really established as we know it until 1956. President Dwight Eisenhower’s support of the Federal-Aid Highway Act helped established the program for funding and building the interstate highways. Many people believe the interstate system was created to only move troops easily across the country. According to the Federal Highway Administration, President Eisenhower’s support of the interstate system was based largely on civilian needs. Needs such as support for economic development, improved highway safety, and congestion relief, as well as reduction of motor vehicle-related lawsuits. The president understood the military value of the Interstate System, as well as its use in evacuations, but that was only part of the reason for his support.
By the way, here is a fun fact you can share with your friends: Interstates or US highways with odd numbers run north-south, while even numbered run east-west. For north-south routes, the lowest numbers begin in the west, while the lowest numbered east-west routes are in the south.
Denver7 traffic anchor Jayson Luber says he has been covering Denver-metro traffic since Ben-Hur was driving a chariot. (We believe the actual number is over 20 years.) He's obsessed with letting viewers know what's happening on their drive and the best way to avoid the problems that spring up. Follow him on Facebook, Twitter or Instagram or listen to his Driving You Crazy podcast on iTunes , Stitcher , Google Play or Podbean.