I'm planning a loop from Spokane, WA to Mullan, ID on 23cc road tires. I'll be picking up the Trail of the Coeur d'Alenes in Plummer on the way out, but need a more direct route back. The Trail of CdA's will take me back as far as Cataldo, and then Canyon Rd parallels I-90 to near exit 34. I can't pick up the North Idaho Centennial Trail until near exit 22. My question is: Is the stretch of I-90 between exits 34 and 22 in north Idaho legal for cyclists? Secondary to that question is: Assuming it is legal, is it safe or advisable?

Thanks for your help and advice!