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State Speed Limits

Colorado law establishes speed limits for roads and highways within the state.  The Colorado Department of Transportation (CDOT) and local authorities may change the speed limit for any road under their respective jurisdictions if the department or local authority determines that the speed limit established by law is greater or less than what is reasonable or safe for road or traffic conditions.  Neither CDOT nor any local authority, however, may increase the speed limit above 75 miles per hour (mph) on any highway.  The table below provides speed limits on Colorado roadways.

State Speed Limits

Type of Road or Highway

Speed Limit

Narrow, winding mountain highways, or blind curves

20 mph

Any business district

25 mph

Any residential district

30 mph

Open mountain highways

40 mph

Open highways that are not a part of the interstate system and are not four‑lane freeways or expressways

55 mph

Surfaced, four‑lane highways that are a part of the interstate system or expressways

65 mph

Source: Section 42‑4‑1101, C.R.S.



If hazardous conditions exist on a roadway, Colorado drivers must slow to a reasonable and prudent speed, although this may require driving at a speed below the posted limit.  Colorado law also grants cities and towns in the state authority to adopt maximum speed limits for their jurisdictions.  CDOT and local authorities may also set minimum speeds.  Colorado law prohibits motor vehicle operators from driving at such a slow speed that they impede the normal and reasonable forward movement of traffic, unless their slow speed is necessary for the safe operation of the vehicle.  In these situations, the driver must drive in the right‑hand lane if there is one available on the roadway, or pull off the roadway when possible to allow any impeded traffic to pass.

In addition, Colorado law prohibits driving on a 6 percent uphill grade of I‑70 at a speed that is less than 10 miles per hour below the speed limit or less than the minimum speed set by CDOT, except if necessary to:

  • obey traffic control devices;
  • enter or exit I‑70;
  • compensate for weather or traffic conditions; or
  • navigate a lane closure or blockage. 

Also, current Colorado law states that a driver must move over or reduce and maintain a safe speed when overtaking an emergency, tow, or public utility vehicle.  Safe speed, if conditions allow, is defined as:

  • 25 miles per hour (mph) if the speed limit is less than 45 mph; or
  • 20 mph less than the speed limit if the speed limit is 45 mph or higher.

CDOT is required to post signs notifying drivers of the restriction.

The effective date for bills enacted without a safety clause is August 7, 2024, if the General Assembly adjourns sine die on May 8, 2024, unless otherwise specified. Details