At Augst, the motorway splits, with the A2 branching off and the A3 continuing past Rheinfelden and Frick. After the Bözberg tunnel is the Birrfeld Motorway Fork, near Birmenstorf. Here, the A1 and A3 share the same route as far as Motorway Interchange Limmattal, where the A3 goes towards Urdorf and the Uetliberg Tunnel which was opened on May 4, 2009. After Zürich the motorway weaves through the hills of the south-east bank of Lake Zürich. It continues along the Walensee (Walen Lake), and on to Mels where it ends at a junction with the A13.