Need for chains has little or nothing to do with the amount of snow: its all about the character of the layer between the rubber and the road. I have been driving shuttles to and from and around a ski resort in the Front Range - everything from E-350 vans to 60-passenger Freightliners - and just when I think I have seen it all: Two weeks ago, a couple of hours into a storm, with less than an inch of accumulation on a previously clear, dry shelf road, very much like the Whitney Portal road, 3 Denver RTD vehicles (two buses and the wrecker sent to save them) received a total of 4 tickets for not chaining up. For good reason: that 1 inch of champaign powder might as well have been an inch of lithium grease, under those particular temperature and grade conditions. Dozens of 4wd, awd and fwd vehicles, both above and below the stuck buses, were just turning around and heading back down. The two buses combined blocked the road for a total of two hours. But don't cry for me, Argentina: it was such a good powder blast that we parked to capacity for two days anyway, but you do NOT want to be the one blocking traffic on the shelf road to a major attraction. Chain up.