Do you get icy-freeze-thaw conditions? Here in DC, we don't get a ton of snow, but when we do get winter weather, it's always just at freezing, so everything immediately gets thawed and re-frozen into ice. Most of my trips to Scotland have been summer, so only had snow up Glen Shee. The one time I visited in winter, it snowed a bit as I drove between Laggan and Dunkeld, but nothing dangerous.