US6, I assume you mean Loveland Pass, is usually closed in winter...hazardous cargoes are allowed over, weather permitting, so as not to stop traffic in the adjacent Eisenhower Tunnel; however, I70 through the Colorado Rockies has rockslides, animals on the highway, extreme grades, extreme weather, avalanches, torrential rains,flash floods, horrendous lightning storms, whiteout blizzards, OUT-OF-STATE drivers lol and who knows what else. Not scary, indeed...from a Denver resident since 1965
I’ve coasted from the Tunnel to Denver many times in all sorts of weather and traffic. Not lately though.
US6 over Vail Pass (back in the day), in traffic, caused me the most close calls. Loveland Pass looks scary though and certainly freaks out my wife.