Colorado's specific passing-lane law is found in Colorado Revised Statutes §42-4-1013.
On a highway where the speed limit is 65 miles per hour or more, a driver generally may not operate a motor vehicle in the passing lane unless the driver is passing another vehicle traveling in a nonpassing lane, preparing to turn left, or the volume of traffic prevents the driver from safely merging into a lane to the right.
For purposes of the statute, the passing lane generally means the farthest-left lane when two or more adjacent lanes of traffic are moving in the same direction.
If the farthest-left lane is restricted to high-occupancy vehicles or is designed only for left turns, the passing lane is the lane immediately to the right of that restricted lane.
Colorado's rule is therefore stronger than a general slower-traffic keep-right requirement. On qualifying highways, the left passing lane is not intended for continuous travel when the driver is not actively passing and can safely move to the right.
Colorado also has additional left-lane restrictions for certain commercial vehicles on specified portions of Interstate 70.
Exceptions
- Overtaking and passing another vehicle traveling in a nonpassing lane.
- Preparing to make a lawful left turn.
- Traffic volume prevents the driver from safely merging into a nonpassing lane.
- A restricted HOV or left-turn-only lane changes which lane legally qualifies as the passing lane.
Penalties
A violation of Colorado's passing-lane law under §42-4-1013 is a class A traffic infraction.
The total amount due may include the applicable traffic fine, surcharge and other court-related assessments. Drivers should verify the current amount shown on the citation or with the court handling the case.
Official Source
Last verified: October 10, 2026