It is the lack of sleep, especially professional drivers (cab drivers) on long journey tend to suffer from too little sleep and likely to doze off for a brief period resulting in crash.
Carelessness and some craps coming in wrong lane... Also some people are not able to control their vehicle at high speed even then they do it.
the hot girls on road sides even called street candid, they are the biggest reason of accidents even I met with such kind. like here is one:
Everybody tends to associate the word accident with driving. How about other accidents such as oil spills and such?