On a stretch of A31 not far from the Dutch border, two sedans got into a "harmless fender bender" in heavy fog. A German newspaper report said traffic isn't normally heavy there, so it could have taken a few minutes as 50 more cars plowed into that original incident.
Two of the deaths occurred after two drivers left their cars and perhaps sought safety behind a guardrail; they were found under another car that had flipped the barrier. The final fatality was found in his car that had slid down an incline beside the road.
"Autobahn" describes any German highway and most are speed limited, so this isn't necessarily about unrestricted speed. Investigators don't yet know what caused the accident, but another German report claims that police are investigating for potential manslaughter charges.