Yes, Old climbs straight up, New winds around, and thus isn't as steep.
But on a couple of grades in Idaho, the Old is the slow and curvy one. Model T's did not have that great of a power to weight ratio. In fact if the road got too steep, they had to back up. Reverse was a lower gear. And gravity feed of fuel worked better if the gas tank was higher.
But apparently this grade dates from stage coach days - when the passengers walked up to save the horses.
http://www.uniondemocrat.com/localnews/4523876-151/closures-planned-for-notoriously-steep-old-priest-grade“With the onset of GPS, people don’t read signs any more,” York said. “You can sit up there on the patio at Priest Station and watch them come up the new grade, then they turn left and go down the old grade. They’re in RVs and buses and they are not even thinking about which way it is to Yosemite. They are just listening to the magic voice coming out of their phones.”
“The reality is we keep seeing head-on and sideswipe collisions,” he said. “People think they can get over out of the way but they can’t. I write tickets for crossing over the yellow lines all the time.”
