as an experienced driver, one drives to the conditions one finds oneself in, posted speeds on highways/freeways for example are for normal dry conditions so if its raining or snowing or blowing a strong gail a driver adjusts his speed accordingly, the same goes for mountainous terrain it always amazed me just how many drivers choose not to put their truck in a suitable low gear while descending a mountain range especially when there's signs on the road stipulating this requirement.