I've seen people double-flat on paved roads, either hitting potholes, glass, expansion joints... just not paying attention. There's been a few crashes here with people riding in groups... I wasn't involved so I can't say what happened, but I haven't heard of anyone crashing on gravel on our rides since I've been around. There's been gravel sections on some of our routes since before I was member. Avoiding traffic is the first 'tenet' in our route design guidelines and personally I worry much more about being struck and killed by a motorist than I do crashing. Our schedule has many brevets that don't have any gravel and many people have asked to have more gravel events on the calendar. All the routes I design have the gravel clearly, and correctly, marked on rwgps... pretty easy for riders to avoid those routes if they don't like riding gravel.