The buses and heavy trucks navigate this road, as this is the only route available in the area. Buses crowded with locals go in any weather, and try to beat the incoming traffic to the curves.It does not help that the fog and vapors rise up from the heavily vegetated valley below, resulting in almost constant fogs and limited visibility. Plus the tropical downpours cause parts of the road to slide down the mountain.
Source: www.darkroastedblend.com