Riding 2-abreast: when and where it is permitted?

A friendly bike educator sent us the following inquiry:

"Hi, Megan:

We have been teaching the Bicycle Friendly Driver course to hundreds of people in Northern Colorado and it has been really well received.  A student in a class the other day brought up a point about side-by-side riding.  He went away and did some research and then wrote the following to me.  I’m hopingyou might be able to provide some clarification so that we are providing accurate information.

 Here’s what the person wrote:

-One of the behaviors cyclists do that upsets car drivers the most is riding side-by-side.  I felt the way this was conveyed in the class was a bit confusing, and might fuel the contention. 

    -What I heard you say was that if cyclists are being overtaken by faster traffic, they need to ride single-file.

    - What I had learned was that if cyclists were impeding the flow of traffic from behind by riding side-by-side, they needed to merge into single-file.  In other words, if there is a clear view ahead to allow cars to stray out of their lane to give a pair of cyclists a minimum of 3 feet, then it was Ok to ride side-by-side.

    -In reading the Statute [ ] it says:

        “Persons riding bicycles or electrical assisted bicycles two abreast shall not impede the normal and reasonable movement of traffic and, on a laned roadway, shall ride within a single lane.” 

I’m not sure what that means.  If one cyclist is on the shoulder and their buddy riding next to them is just inside the traffic lane, are they riding within a single lane?  When is it Ok to ride side-by-side?I appreciate any info you can provide!  Thanks, Megan.

First let's start with an analysis of the statute and its actual language.  We don't get to question why the legislature does what it does, we have to live with the actual words contained in the law.  Often times, a strict reading of the law can provide answers, but not always.  

C.R.S. 42-4-1412(6) addresses when cyclists may ride two abreast:

(6)(a) Persons riding bicycles or electrical assisted bicycles upon a roadway shall not ride more than two abreast except on paths or parts of roadways set aside for the exclusive use of bicycles.

(b) Persons riding bicycles or electrical assisted bicycles two abreast shall not impede the normal and reasonable movement of traffic and, on a laned roadway, shall ride within a single lane.

Reading the two sections together, I conclude the following:

-Cyclists may not ride MORE than 2 abreast, unless they are somewhere exclusively for bikes (which would really only be a bike lane).  Anywhere else, 2-wide is the absolute legal max. 

-Cyclists may only ride 2 abreast IF they are not impeding the normal/reasonable movement of traffic. If the cyclists riding 2 abreast ARE impeding traffic, the implication here is that they ride single file!

What does "impede" mean for purposes of this section?  I'll share some thoughts i've learned from law enforcement:

a) I know it when I see it.  Impeding = cyclists 2 abreast are causing traffic congestion, cars are backed up, there is a traffic jam/chaos; or

b) many sheriffs offices have a loose standard of 5 or more cars backed up behind the cyclists riding 2 abreast = impeding traffic.

Next- The Statute Definition section defines roadway:

(89) "Roadway" means that portion of a highway improved, designed, or ordinarily used for vehicular travel, exclusive of the sidewalk, berm, or shoulder even though such sidewalk, berm, or shoulder is used by persons riding bicycles or other human-powered vehicles and exclusive of that portion of a highway designated for exclusive use as a bicycle path or reserved for the exclusive use of bicycles, human-powered vehicles, or pedestrians. In the event that a highway includes two or more separate roadways, "roadway" refers to any such roadway separately but not to all such roadways collectively.

Now - to address the questions asked above:

-Being overtaken by faster traffic does not, by itself, mean riders need to go single file.  Riders need to single up if their riding side-by-side is impeding traffic. 

-If an overtaking car is able to pass the 2-abreast cyclists safely with the 3-foot passing distance, this is not impeding traffic.  If the riders become aware of vehicles behind them unable to pass, then the cyclists would be well-advised to single up. 

-What about one cyclist on the shoulder and one in the roadway? Well -let's reference the definition above.  Roadway EXCLUDES shoulder.  The statute governing 2-abreast riding refers to roadway.  Therefore reading the two together, if one cyclist is on the shoulder and one is in the roadway, this legally = one cyclist on the roadway (as the law would disregard the cyclist on the shoulder for purposes of the 2-abreast analysis).  The same would be true if one rider is in the bike lane and one is in the roadway.  Though legal, this is not always advised- it is preferable for the 2 riders to ride side-by-side in the bike lane, since that is an established place created for them to ride, and it therefore frees up the traffic lane for cars.  NOTE however: there is no legal requirement that mandates cyclists MUST ride in a bike lane where it exists.  

My suggestion: If a rider is so new or inexperienced as to be uncomfortable riding closely to a cyclist next to them, it is advisable to simply ride single file.  We are looking for a pretty tight two-by-two formation in application of this concept to make it possible for cars to pass (and to give 3 feet!).  Practice riding close side-by-side with your mates in parks or quiet streets or bike paths, to develop this skill.  Most bike lanes and shoulders are wide enough for two cyclists to ride next to one another and then you can remain social with your riding partners without needing to be in the roadway at all!