5foot5 But that is just a technicality because in pratice the cyclists behave like they are racing against each other
No, its not just a technicality. In time trials, cyclists are not allowed to draft off each other (take shelter by riding behind), or ride in packs - it must be individual effort, or they will be disqualified. There is great cache in catching and overtaking your "minute man" - cyclists are usually sent off at one minute gaps. The rule book prescribes how to overtake and you have to do it quickly, or said drafting will occur.
Group riding is probably training rides or non-competitive sportives, both of which are allowed on roads because unless they are motorways, all sorts of road users are allowed to share them with cars.
Road races require police sanction. Unlike on the Continent, where the police hand over the control of the roads to the race organisers. It really is a wonderful atmosphere, to go along to a cycling race in Belgium or France, where the town centre is closed to traffic and theres usually a funfair, lots of food, tombola, etc.. Great atmosphere while waiting for the cyclists to return from their route.
I feel guilty when driving on a road full of cyclists - I mainly run for exercise now but used to do much more cycling. I am far more frequently held up by other vehicles when driving than cyclists, far far more. Life would be so much simpler if there weren't any busses, dithery doddery drivers, women putting their make up on and missing green lights, slow old cars, etc.. Sadly I cannot dictate who else uses the roads!