[rodary]

Paceline has nothing to do with road closures.

Riders form a paceline because of the crosswind which forces everyone to look for draft on the left or the right side of a rider in front of you. Eventually, there's not enough road for everyone to be in the draft and the first paceline is formed (also called an echelon).

More specifically though, paceline refers to the mechanics of the echelon, the way riders rotate, or take turns at the front to stay in the echelon. This rotation is the paceline.

[PaulDavisThe1st]

Pelotons - the race variety of a paceline - can only be safely formed with road closures because they typically swell to fill at least one lane of the road. They are not just 1 rider behind another, but often 2-4 riders wide.

Pacelines for group rides and the like can be formed whenever, and they do not form just because of a crosswind. When I used to train with a group, we would almost always form pacelines in single file, on every ride.