Many good comments. In my 50's, I started from the ground floor and ended up riding with the fastest groups I could find. I noted two things over this time. 1. Rider category - Riding in the "C" or lower categorized rides always seemed pretty safe. Minimal testosterone, and everyone watching out for each other. The "B" rides were the most dangerous - high levels of testosterone and marginal safety. The "A" rides were great - everyone very experienced and dialed in. I worked my BUTT OFF (literally, ask my wife…) to improve to an "A" level, and above. 2. Group size - I found that 2-7 riders was the best size in most instances. Riding alone makes you less visible to drivers, and other riders can help if you have a problem. Also, I enjoy company when I'm riding. Larger groups, always seemed to be more dangerous (in my opinion). I did enjoy riding in pace lines with larger groups, but only when the riders all were racers, or race equivalent in attention to their surroundings.

I've been dropped on more group rides than I can count, but the only times that I've left a group ride for safety reasons were on "B" rides.