I think for most people, having a good winter kit in the vehicle for shelter in place scenarios is more common. There are not too many roads where there is no traffic and you would be forced to walk.
The more common scenario is where the highway is shutdown due to weather, traffic accident etc for hours on end and having the appropriate kit in the vehicle gives a lot more warm and comfort options. Also it would save from having to run the vehicle engine as much in an attempt to stay warm.
Case in point. This past weekend on Saturday, a major and only north-south highway was completely closed for
10 hours due to an accident with 2 fatalities. Depending on where you were stopped on the road, some were able to get turned around and head south back to the metro area or north to another town or Whistler Ski Village further north.
Others who stayed and waited in their vehicles for those long and cold hours where temps were just at the freezing level were probably wishing they had a decent winter kit in their vehicles.