WATCH: Horrifying coach crash

Footage captured by a passing motorist shows the sickening moment that a coach crushed five cars after the driver allegedly fell asleep at the wheel. Vehicles were backed up while queuing to enter a tunnel on the motorway in Yeongdong, South Korea, when the bus piled into them at full speed.

According to local news reports, four people were killed instantly in the horror smash while another 37 passengers sustained serious injuries.