But usually yes. You either need to have 4x4 or chains. they have signs that turn on when the road conditions are sketchy. There are always a buncha cops up the canyons too so prolly not worth it to not chain up/ have all wheel drive.
yea it says "4x4 or chains required" on the snowy days. as for when that is, alta's website has the status of the road in their weather section. chains fucking suck I'd recommend finding a friend with awd to take ya when possible.
I have a FWD with snowtires, and I have chains in the trunk at all times. They have never actually made me put the chains on, but I had to have them cause its required. The cops up there patrolling were cool with it.