Highway 550 is a mountain road with steep sections. However, people with trailers do it all the time, as do semis and buses . I don't know if I'd do it if I was a flatlander. And the worst section of the road is probably the section that drops down into Ouray...steep and windy. They don't call Ouray "Little Switzerland" for nothing. But if you have good brakes, it's a gorgeous drive.