This guide is for general information only and is not legal advice. Laws change — verify current rules with your state DOT or a licensed attorney before relying on this for any legal matter. Read full disclaimer.
The rule
Bicycles are permitted on Interstate highways in Colorado. CDOT permits bicycle travel on the paved shoulders of rural Interstate segments where no reasonable alternative exists, including most of I-70 west of Denver and large portions of I-25 and I-76. Urban Interstate segments through metro Denver, Colorado Springs, and Fort Collins are signed prohibited, as are the Eisenhower–Johnson tunnels on I-70 (a designated cyclist shuttle is provided).
What this means in practice
Interstate cycling is legal in Colorado, but ride only where you have a wide, clean shoulder and exit at the first signed bicycle exit when conditions deteriorate.