Boulder County piloting new road signs to improve bicycle safety

From Boulder County

Feedback from road users on the new signage is encouraged

Boulder County, Colo. – To help improve safety for all roadway users in the plains/flatland areas, Boulder County will be piloting new signs to remind motorists and bicyclists about the rules for passing on county roads. These signs will be piloted on roads with significant vehicle and bicycle traffic that also do not have shoulders. These are roadways where motorists typically need to cross the centerline to give bicyclists the necessary three feet of space.

Boulder County has begun installing “STATE LAW/ 3 FEET MINIMUM” signs on roads near Hygiene and Lyons to remind motorists to give cyclists three feet of clearance when passing. The three feet of space is measured from the widest part of the vehicle (typically the mirrors or a trailer) to the cyclist and provides a margin of safety for bicyclists to maneuver around obstacles in the roadway or debris while being passed by a motorist. These signs will be printed on a white background, which means that, like speed limit signs, they are regulatory and must be obeyed.

Many times motorists are unsure how to safely pass bicyclists with the required three feet on narrow roads without shoulders. In Colorado, when it is safe, there is adequate sight distance and it would not interfere with oncoming traffic, motorists can cross a solid yellow line (in what is otherwise a no passing zone) to safely pass a cyclist. If there is inadequate sight distance, such as around a curve or before an upcoming hill, or if there is oncoming traffic, motorists must slow down and wait until it is clear to give a cyclist three feet of clearance when passing.

To remind drivers and bicyclists of the rules, Boulder County is also installing “WHEN SAFE MAY CROSS SOLID YELLOW TO PASS BIKES” signs and placards on the same roads that receive the “Three Feet Minimum” signs. This sign will be printed on a yellow background, meaning they are advisory and not regulatory.

“Often there tends to be confusion by both drivers and bicyclists on what the state law says about when and how to pass a bike rider,” noted Boulder County Transportation Director George Gerstle. “Our goal is to improve safety and reduce tension between all users of the road by providing clarity, so everyone can know what to expect from each other.”

To help develop the new signs, Boulder County Transportation and the Sheriff’s Office worked with Cyclists 4 Community (C4C), a local non-profit focused on improving motorist-cyclist relationships and safety for all roadway users.

“Cyclists 4 Community’s goal is to raise awareness for both cyclists and motorists about safe use of the roads,” stated Ed Kuh with C4C. “Our target is to have zero deaths or serious injuries as a result of motorist/cyclists conflicts or collisions. Along with improved riding and driving habits, having the ‘three feet passing’ signage will help.”

The new signs are being installed on a trial basis and Boulder County welcomes feedback. Please send comments to or call 303-441-3900. You can also complete an online survey.

Prior to the 2013 Flood, Boulder County (at the suggestion of a motorist and bicycle working group) installed signs advising cyclists to ride single file in curves and reminding motorist to pass with care in the mountain canyons. These signs were placed particularly on mountain roads that see heavy cycling traffic and have limited sight distance and no shoulders. As part of flood reconstruction efforts, Boulder County has installed signage advising cyclists to ride single file on mountain roads that are either already under, or awaiting, reconstruction.

Signage shown on the roadside


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