The car association predicted a chaotic week on the nation's roads, with school holidays kicking off in North Rhine-Westphalia, Bavaria and Baden-Württemberg. Families from north-eastern states have to start heading home as their summer break comes to an end.
The resulting traffic will likely cause long, gridlocked queues in both directions by Wednesday on Germany's main routes, warned the ADAC.
Bavaria goes on holiday on Wednesday, while in Hamburg, Berlin, Brandenburg, Bremen and Mecklenburg-Pomerania, Schleswig-Holstein and Lower Saxony, the summer break is almost over.
The club warned that the gridlock won't be confined to Germany, but more or less a whole band of central Europe as motorists from all over the continent travel to and from holiday destinations.
Queues are expected this week in motorways in Austria, Switzerland, Italy, France, Slovenia and Croatia, it said.