[avereveard]

multicar crash happens 1/cars times, duh, they account for the same fatalities but you are far less likely to be in one, because they are tied to exceptional events (i.e. snow) and non uniform across the population.

[watwut]

Snow is not exceptional event. Nor is rain.

And while multi car crashes happen less often, they involve more cars, so if don't affect you chance to not get into one.