You're new here, ZenS, so I want you to know that none of the people you describe in your last paragraph are posting here. You should do a search on the topic, and give a little more credit to people who have been here longer, and who have fought some of the battles with cars and governments over this issue.

I don't see why the single file rule applies on a 4-lane road. It's probably illegal to pass any vehicle in the same lane if there is a perfectly good, open lane in the same direction just to your left, anyway.

That cop was just an idiot to step out in front of the peloton and cause a wreck. Trying to stop a peloton is kind of like trying to stop a freight train. The lead riders might be able to see what's going on, but the rest of them are going to pile up behind because they aren't given the same opportunity to see and hear what's happening up ahead. Shorter reaction time. If the cop really couldn't predict the consequences of his/her actions, maybe this is not the right field.

The peloton should stop when asked, immediately. Not cooperating with the police only leads to more problems. But, it doesn't appear they were asked in this instance.

Karen