The two halves of the autobahn each traverse one tunnel and a series of two or three viaducts that were designed by Paul Bonatz and built for the Reichsautobahn; the bridges were all destroyed in World War II and had to be rebuilt, and the route in one direction was only completed in the 1950s.

The separated sections, which are some 2 kilometres (1.2 mi) apart at the furthest and over which the autobahn rises or descends 230 metres (750 ft), lie between Mühlhausen im Täle and Hohenstadt, where there is an emergency access road.

The impact of large supports under a four-lane structure on the beauty of the landscape was also a consideration, as it had been in the Aichelberg section, which was built stacked to minimise this.

[3] The northbound carriageway was completed in record time and opened on 30 October 1937 carrying traffic in a single lane in each direction.

[6] The almost finished Lämmerbuckel Tunnel was then closed at both ends with heavy gates and used for production of aircraft engines and other armaments by Heller and Daimler-Benz; heating, lighting and living quarters were provided inside.

[7] The southbound carriageway was finally completed in 1955–57, with work including completion of both viaducts, creation of the road bed and retaining walls (using concrete, rather than the paving stones and masonry that had been used for the northbound section),[6] and installation of bomb shelters in the Lämmerbuckel Tunnel, which when the segment finally opened on 25 May 1957, was the longest motorway tunnel in Europe.

[13] The plan is now indefinitely postponed, although it was listed as a priority for use of construction funds in the 2011–15 period by the German Minister of Transport, Peter Ramsauer.

[14][15] In 2011, the Lämmerbuckel Tunnel was completely renovated, including replacement of the wall tiles installed in the 1950s by moisture-resistant concrete and improvement of emergency facilities.