Ride etiquette

every time the leaders rotate, it becomes 4 abreast for the duration of the changeover, it's not mentioned but would seem to take some skill and judgement to know when is the right time, and what to do if other vehicles/road conditions become less than ideal mid-change.

Rotating paceline is better ideal than this.

See

http://www.lostrivercycling.org/paceline.html