Autobahn

The Autobahn (IPA: [ˈaʊtoˌbaːn] ^ⓘ; German pl. Autobahnen, pronounced [ˈaʊtoˌbaːnən] ^ⓘ) is the federal controlled-access highway system in Germany. The official term is Bundesautobahn (abbreviated BAB), which translates as 'federal motorway'. The literal meaning of the word Bundesautobahn is 'Federal Auto(mobile) Track'.

Much of the system has no speed limit for some classes of vehicles. However, limits are posted and enforced in areas that are urbanised, substandard, prone to collisions, or under construction. On speed-unrestricted stretches, an advisory speed limit (Richtgeschwindigkeit) of 130 kilometres per hour (81 mph) applies. While driving faster is not illegal in the absence of a speed limit, it can cause an increased liability in the case of a collision (which mandatory auto insurance has to cover); courts have ruled that an "ideal driver" who is exempt from absolute liability for "inevitable" tort under the law would not exceed the advisory speed limit.

A 2017 report by the Federal Road Research Institute reported that in 2015, 70.4% of the Autobahn network had only the advisory speed limit, 6.2% had temporary speed limits due to weather or traffic conditions, and 23.4% had permanent speed limits. Measurements from the German state of Brandenburg in 2006 showed average speeds of 142 km/h (88 mph) on a 6-lane section of Autobahn in free-flowing conditions.

Only federally built controlled-access highways with certain construction standards including at least two lanes per direction are called Bundesautobahn. They have their own white-on-blue signs and numbering system. In the 1930s, when construction began on the system, the official name was Reichsautobahn. Various other controlled-access highways exist on the federal (Bundesstraße), state (Landesstraße), district, and municipal level but are not part of the Autobahn network and are officially referred to as Kraftfahrstraße (with rare exceptions, like A 995 Munich-Giesing–Brunntal until 2018). These highways are considered autobahnähnlich (autobahn-like) and are sometimes colloquially called Gelbe Autobahn (yellow autobahn) because most of them are Bundesstraßen (federal highways) with yellow signs. Some controlled-access highways are classified as "Bundesautobahn" in spite of not meeting the autobahn construction standard (for example, the A 62 near Pirmasens).

Similar to some other German words, the term autobahn when used in English is usually understood to refer specifically to the national highway system of Germany, whereas in German the word autobahn is applied to any controlled highway in any country. For this reason in German, the more specific term Bundesautobahn is strongly preferred when the intent is to make specific reference to Germany's Autobahn network.

Similar to high-speed motorways in other countries, autobahns have multiple lanes of traffic in each direction, separated by a central barrier with grade-separated junctions and access restricted to motor vehicles with a top speed greater than 60 km/h (37 mph). Nearly all exits are to the right; rare left-hand exits result from incomplete interchanges where the "straight-on" leads into the exit. The earliest motorways were flanked by shoulders about 60 centimetres (24 in) in width, constructed of varying materials; right-hand shoulders on many autobahns were later retrofitted to 120 centimetres (47 in) in width when it was realized cars needed the additional space to pull off the autobahn safely. In the postwar years, a thicker asphaltic concrete cross-section with fully paved hard shoulders came into general use. The top design speed was approximately 160 km/h (99 mph) in flat country but lower design speeds were used in hilly or mountainous terrain. A flat-country autobahn that was constructed to meet standards during the Nazi period could support speeds of up to 150 km/h (93 mph) on curves.

The current autobahn numbering system in use in Germany was introduced in 1974. All autobahns are named by using the capital letter A, which simply stands for "Autobahn" followed by a blank and a number (for example A 8). The main autobahns going all across Germany have a single-digit number. Shorter autobahns that are of regional importance (e.g. connecting two major cities or regions within Germany) have a double-digit number (e.g. A 24, connecting Berlin and Hamburg). The system is as follows:

There are also some very short autobahns built just for local traffic (e.g. ring roads or the A 555 from Cologne to Bonn) that usually have three digits for numbering. The first digit used is similar to the system above, depending on the region.