Only one person slightly eluded to this so wanted to bring it up...
Sounds like you possibly have no experience driving the mountains out west and that is fine and is good you are asking. There has been good information mentioned in the responses but also, please make sure you are being considerate by using right lanes and turnouts when you are the slower vehicle on the road. Many mountainous roads have limited amounts of lanes and it is considered a good driving habit to be aware of others on the road, being considerate in the process using right lanes/turnouts.
Thanks and enjoy your trip!