This is an old question that is no longer in use.
Images may be missing and the information may be dated.
It is winter, and it has been snowing for several days. Which alternative applies to junctions?
Many cars will stop and start at a junction. This compacts the snow, which makes it slippery and thereby means it provides less traction.
Ploughing can make the problem worse, as this removes the loose snow and leaves only the compacted icy snow, which is practically impossible to get rid of.
More examples of explanations: