Primary cause of most accidents is lack or poor situational awareness of surroundings for a variety of reasons, including driving under the influence of mind/reaction altering substances. Higher the speed and greater the differential in speed between automobiles involved in an accidents, more the damage.
It would seem unbelievable to drivers in US but in general, we have far less situational awareness on roads here than good drivers do in Asia for simple reasons that in Asia, they have to account for and react to the insanely absurd behavior and actions of others from all around them, and still manage to complete the trip unscathed. Majority of the average US drivers who may consider themselves to be a safe driver here, wouldn’t survive a week of driving in a big city in Asia without getting involved in an accident.