A bus carrying German retirees plunged off a highway and rolled Tuesday, killing at least four and injuring more than 40, dpa cited police as saying. Police said a skidding car seemed to have knocked the bus off Germany's Autobahn 4, about 100 kilometres north-east of Frankfurt. A police spokesman said the bus broke through a roadside crash barrier, fell down a bank several metres wide and came to rest on its wheels 50 metres from the highway, apparently after overturning, in the mid-morning crash.