In relation to the rest of the line, the Wienerwald Tunnel formed only one element of a wider complex of tunnels. Towards the eastern end (nearest Vienna), it meets with an underground junction with another 2.2 km tunnel, carrying two extra tracks for the old Westbahn, which has been operational since December 2008, and direct tracks across the junction continue in the Lainzer Tunnel, a 12.3 km long twin-track single tube tunnel that was constructed in parallel with the Wienerwald Tunnel. When combined with the adjacent Lainzer Tunnel, the Wienerwald Tunnel results in trains covering an underground distance of 26 km, making it Austria's longest tunnel.