The 11 fatalities in the Trakia highway pile-ups make the Bulgarian crashes the deadliest major multi-vehicle collision involving dozens of vehicles recorded in Europe since 2016, despite several other European accidents involving even larger numbers of vehicles. Dense fog is a common element in the Trakia highway disaster and several of Europe's largest pile-ups. Other major crashes have been triggered by sudden hailstorms, icy roads, snowfall or an abrupt loss of traction. ...