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What's Driving You Crazy?: The two separate Colorado Boulevard exits on I-70

"I thought exit names must be unique in any one state"
Colorado Blvd Denver
Colorado Blvd Idaho Springs
Posted at 5:05 AM, May 04, 2021
and last updated 2021-05-05 06:07:22-04

Mark from Golden writes, “What’s Driving You Crazy? Hi, Jayson. Why are there two Colorado Boulevard exits in the state of Colorado? There’s one in Denver, obviously, but there’s also one in Idaho Springs on westbound I-70. I thought exit names were to be unique in any one state.”

This is one of the most interesting questions I have received over the years. There is no official requirement in Colorado, or the United States, where exit names have to be unique to one location, although most are.

In Colorado, there are two distinct Colorado Boulevards with two distinct and separate exits along I-70. Bob Wilson with CDOT tells me a city, town or county has the responsibility for naming their roadways and if an interchange is required for that roadway, that name will usually be the one used to designate the interchange or exit.

One key reason that similarly named major roadways are never geographically close to each other is due to potential confusion to drivers, the U.S. Postal Service, and others. In this case, the two Colorado Boulevard exits are 35 miles apart, so the risk of confusion is literally non-existent. Each have separate mile marker designations. Mile marker 241 for Idaho Springs and miler marker 276 for Denver’s Colorado Boulevard. Plus, each of these same named roads run in different directions: east/west in Idaho Springs and a north/south through Denver.

Another good example of a same named exits for different roads is on I-25. Near Monument, there’s County Line Road between Douglas and El Paso counties and in the Denver Tech Center, there’s County Line Road between Douglas and Arapahoe Counties. Wilson says, when necessary, CDOT distinguishes each road, such as when adverse weather closes I-25 and they need to be clear about which County Line Road they are referencing, minimizing confusion.

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Other commonly named roadways with more than one interchange on the interstate system, not just through Colorado but in other states, include Main Street and Broadway. County Line Road is the most common named interstate interchange within Colorado.

There are instances where the same road crosses the interstate in two different locations with different exit numbers. In Colorado Springs I-25 crosses Academy Boulevard twice on the north and south sides of the city, about 15 miles apart at exits 150 and 135. In metro Denver, Colfax Ave crosses I-70 twice east and west of the city, about 26 miles apart at exits 288 and 262.

Bob Wilson with CDOT added this historical fact about Colorado Boulevard through Idaho Springs: He says Colorado Boulevard was part of the state highway system until just a few years ago and was the first section of the interstate constructed west of Denver. It went from the bottom of Floyd Hill at the junction of US 6, through the Twin Tunnels, through south Idaho Springs to the west end of town. At one point Colorado Boulevard in Idaho Springs was the I-70 Business Route but CDOT gave up ownership of it and Colorado Boulevard became an Idaho Springs owned roadway. In 1920, it was U.S. 40 and U.S. 6. In 1938 until 1961, U.S. 6 and 40 were rerouted to the south end of town, where I-70 is located now. It officially received the Interstate 70 identification later in the 1960s.

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.