How did one foggy stretch of Bulgarian motorway become a 12-death pileup?

A fog bank settled over the motorway linking Sofia with Burgas, and the chain of crashes began near Yambol, where dozens of cars and trucks piled up across all six lanes.

The health ministry's later count put the dead at 12, with dozens more injured and some of them in critical condition.

The interior minister, Ivan Demerdzhiev, said visibility fell to 10 metres in very little time, and the road safety institute says the motorway should have been shut from that morning.

European Commission figures show Bulgaria recorded 71 road deaths per million people last year, against 19 in Sweden.