Looking at their own rules: Edit: the rules they suggest: https://www.active.com/cycling/articles/10-rules-to-group-ride-like-a-pro The second one makes sense when it's not a planned event. This video shows the complete opposite, the cyclists take up the entire road, five in width. Which looks a lot like an event, when cars wouldn't be allowed

Wouldn't the road be closed for cars? At least no one died