Mountain pass Grades

I'm looking in "Mountain Directory West". Siskiyou Summit on I-5 southbound is max. 6% downhill for 2.25 m, then 4% for 1.5 m, then 6% for 1.5m, then 4% for 1.25m, then 6% for 1.5 m, then 4% for 2m. There is then an inspection station, "all vehicles must stop". 4 m. after that, 6% descent, then 6% climb for 4 m, then 5% down for 3 miles.

There is no grade information for I-5 in the Mt. Shasta area.

North of Grant's Pass, Oregon, there are four summits. Max descent is 6%. Descent lengths are 3 miles, 2miles, 2miles, and 2 miles on south sides.