I ride chip seal roads a lot, so when you say un ride able, I'm not sure what you mean. As for the roads with a 55 mph limit, well it depends on the amount of traffic, but yes I ride those as well. I have ridden the shoulder of interstate highways where allowed to do so in my area. I try of course to avoid those roads, but sometimes they are all that is available. Good luck, make sure you have a good mirror, or be prepared to look over your shoulder a lot. Lights help, even during the day.