Hwy 75 in Idaho is a scenic byway. It is not straight flat or barren it winds climbs is narrow and scenic. Traffic is slow due to being a two lane river road with Elk deer and other wild animals to look at some of the corners are a 25 mph. So your est. of the time travel for a typical traveler is 1.5 to 2.5 hours off safe passage from Sun Valley Idaho to Challis ID just as an example. We have been 30 years of towing and recovery on this HWY surrounding area. And have found people who come with your type of info to be mislead believeing a quick journey with phone service. This area is in the mountains or should I say wilderness area of Idaho please don't group us with the flatlands. Slow down their visits for safety SAKE. Thank you and come to Idaho in the Mountains of Challis Idaho and see for yourself how beautiful it really is. Willie and Patty Earle