Bundesautobahn 81

BAB intro|81 is an Autobahn in Germany. It branches off the A 3 at the Würzburg-West triangle and ends near the border to Switzerland.

The oldest part of the A 81 between the Weinsberg intersection (A 6) near Heilbronn and the Leonberg triangle (A 8) near Stuttgart was finished in the years 1938 to 1940. This section included the first tunnel built for an Autobahn, the 300 m "Engelbergtunnel" near Leonberg. When Weinsberg-Leonberg was upgraded to 3+3 lanes in the 1970s, the tunnel with its two lanes each and steep grades (up to 6%) became something of a bottleneck. In 1999 a new 2,530 m Engelbergtunnel was opened.

Original plans called for the A81 to be continued beyond Leonberg, but these plans were later abandoned. Instead, the A81 shares a part of the A8 to the Stuttgart intersection and then continues south on a motorway tha was built as A831 to Gärtringen, where it meets the original line again at a partly finished intersection. As a result of this change of plans, Gärtringen became one of the only exits in the German Autobahn network that leaves to the left.

Further south, the terrain required some spectacular engineering, including a 900 m long bridge near Horb that spans 125 m above the Neckar river. Currently, the A 81 ends near Singen.