• German Motorway System Bundesautobahn, 1920
  

Germany's autobahn network had a total length of about 12,845 kilometers (7,982 mi) in 2012, which ranked as the fourth longest highway system in the world behind the National Trunk Highway System (NTHS) of China, the Interstate Highway System of the United States, and the autopistas and autovías of Spain.

These motorways are officially named Bundesautobahn (BAB), as they were built and maintained by the federal government. In the 1920s and 1930s, the official name was Reichsautobahn.

Similar to such 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 of more than 60 km/h (37 mph). The earliest carriageways were flanked by shoulders about 60 centimeters (24 in) in width, constructed of varying materials; right hand shoulders on many autobahns were later retrofitted to 120 centimeters (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 full 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 could be used in hilly or mountainous terrain. A flat country autobahn, which was constructed to meet standards during the Nazi period, could support the speed 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:

• A 10 to A 19 are in eastern Germany (Berlin, Saxony - Anhalt, parts of Saxony and Brandenburg)
• A 20 to A 29 are in northern and northeastern Germany
• A 30 to A 39 are in Lower Saxony (northwestern Germany)
• A 40 to A 49 are in the Rhine - Ruhr Area
• A 50 to A 59 are also in the Rhine - Ruhr Area
• A 60 to A 69 are in Rhineland - Palatinate, Saarland and Hesse
• A 70 to A 79 are in Thuringia, northern Bavaria and parts of Saxony
• A 80 to A 89 are in Baden - Württemberg
• A 90 to A 99 are in (southern) Bavaria

There are also 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 one of which is similar to the system above, depending on the region. East - west routes are always even - numbered, north - south routes are always odd - numbered.

The north - south autobahns are generally numbered using odd numbers from west to east; that is to say, the more easterly roads are given higher numbers. Similarly, the east - west routes are numbered using even numbers from north (lower numbers) to south (higher numbers).

The idea for the construction of the autobahn was first conceived in the late 1920s during the days of the Weimar Republic, but the construction was slow, and most projected sections did not progress much beyond the planning stage due to economic problems and a lack of political support. One project was the private initiative HaFraBa which planned a "car only road" crossing Germany from Hamburg in the North via central Frankfurt am Main to Basel in Switzerland. Parts of the HaFraBa were completed in the late 1930s and early 1940s, but construction eventually was halted by World War II. The first road of this kind was completed in 1932 between Cologne and Bonn and opened by Konrad Adenauer (Lord Mayor of Cologne and future Chancellor of West Germany) on 6 August 1932. The road is currently the Bundesautobahn 555. This road was not yet called Autobahn, but instead was known as a Kraftfahrstraße ("motor vehicle road").

Just days after the 1933 Nazi takeover, Adolf Hitler enthusiastically embraced an ambitious autobahn construction project and appointed Fritz Todt, the Inspector General of German Road Construction, to lead up the project. By 1936, 130,000 workers were directly employed in construction, as well as an additional 270,000 in the supply chain for construction equipment, steel, concrete, signage, maintenance equipment, etc. In rural areas, new camps to house the workers were built near construction sites. The job creation program aspect was not especially important because full employment was almost reached by 1936. The autobahns were not primarily intended as major infrastructure improvement of special value to the military as often stated because they were of no military value as all major military transports in Germany were done by train to save fuel. The propaganda ministry turned the construction of the autobahns into a major media event that attracted international attention.

The autobahns formed the first limited access, high speed road network in the world, with the first section from Frankfurt am Main to Darmstadt opening in 1935. This straight section was used for high speed record attempts by the Grand Prix racing teams of Mercedes - Benz and Auto Union until a fatal accident involving popular German race driver Bernd Rosemeyer in early 1938. The world record of 432 km/h (268 mph) set by Rudolf Caracciola on this stretch just prior to the accident remains one of the highest speeds ever achieved on a public motorway.

Development of the overall length (at the end of):

During World War II, the central reservation of some autobahns were paved to allow their conversion into auxiliary airports. Aircraft were either stashed in numerous tunnels or camouflaged in nearby woods. However, for the most part, the autobahns were not militarily significant. Motor vehicles, such as trucks, could not carry goods as quickly or in as much bulk as trains could, and the autobahns could not be used by tanks as their weight and caterpillar tracks damaged the road surface. The general shortage of gasoline in Germany during much of the war, as well as the low number of trucks and motor vehicles badly needed for direct support of military operations, further decreased the autobahn's significance. As a result, most military and economic freight was carried by rail. After the war, numerous sections of the autobahns were in bad shape, severely damaged by heavy Allied bombing and military demolition. Furthermore, thousands of kilometers of autobahns remained unfinished, their construction brought to a halt by 1943 due to the increasing demands of the war effort.

In West Germany (GFR), most existing autobahns were soon repaired after the war. During the 1950s, the West German government restarted the construction program. It invested in new sections and in improvements to older ones. The finishing of the incomplete sections took longer, with some stretches opened to traffic in the 1980s. Some sections cut by the Iron Curtain in 1945 were completed after German reunification in 1990. Some sections were never completed, as more advantageous routes were found. Some of these incomplete sections to this very day stretch across the landscape forming a unique type of modern ruin, often easily visible on satellite photographs.

The autobahns in East Germany (GDR) after 1945 were neglected in comparison to those in West Germany. East German autobahns were used for GDR military traffic and/or for state owned farming or manufacturing vehicles. The speed limit on the GDR autobahns was 100 km/h; however, lower speed limits were frequently encountered due to poor or quickly changing road conditions. The speed limits on the GDR autobahns were rigorously enforced by the Volkspolizei, whose patrol cars were frequently encountered hiding under camouflage tarps waiting for speeders.

The first autobahn in Austria was the West Autobahn from Wals near Salzburg to Vienna. Building started by command of Adolf Hitler shortly after the Anschluss in 1938. It lengthened the Reichsautobahn 26 from Munich (the present day Bundesautobahn 8), however only 16.8 km (10.4 mi) including the branch-off of the planned Tauern Autobahn had been opened to the public on 13 September 1941. Construction works discontinued the next year, they were not resumed until 1955.

There are sections of the former German Reichsautobahn system in the former eastern territories of Germany, i.e., East Prussia, Farther Pomerania and Silesia; these territories became parts of Poland and the Soviet Union with the implementation of the Oder - Neisse line after World War II. Parts of the planned autobahn from Berlin to Königsberg (the Berlinka) were completed up to Stettin (Szczecin) on 27 September 1936, after the war incorporated as the A6 autostrada of the Polish motorway network. A single carriageway section of the Berlinka east of the former "Polish Corridor" and the Free City of Danzig opened in 1938; today it forms the Polish S22 expressway from Elbląg (Elbing) to the border with the Russian Kaliningrad Oblast, where it is continued by the R516 regional road. Also on 27 September 1936, a section from Breslau (Wrocław) to Liegnitz (Legnica) in Silesia was inaugurated, which is today part of the Polish A4 autostrada, followed by the (single carriageway) Reichsautobahn 9 from Bunzlau (Bolesławiec) to Sagan (Żagań) the next year, today part of the Polish A18 autostrada.

After the German occupation of Czechoslovakia, plans for a motorway connecting Breslau with Vienna via Brno (Brünn) in the "Protectorate of Bohemia and Moravia" were carried out from 1939 until construction works discontinued in 1942. A section of the former Strecke 88 near Brno is today part of the R52 expressway of the Czech Republic.

Today, Germany's autobahn network has a total length of about 12,845 km (2012).

Most sections of Germany's autobahns are modern, containing two or three lanes in addition to an emergency lane (hard shoulder). A few other sections remain in an old state, with two lanes, no emergency lane, and short slip-roads and ramps. Such a combination of the two types of autobahn can be seen on the A 9 autobahn (Munich - Berlin). Heading out from Munich, the autobahn starts off as modern, with five lanes in each direction plus emergency lane. In contrast, parts of the autobahn have only two lanes and no emergency lanes (only rare emergency bays with an emergency telephone post) such as in Thuringia, which was formerly part of East Germany, or most parts of the A 40 in West Germany.

A hard limit is imposed on some vehicles:

The German autobahns are famous for being among the few public roads in the world without blanket speed limits for cars and motorbikes.

Speed limits do apply at junctions and other danger points like sections under construction or in need of repair. Speed limits at non-construction sites are generally between 100 km/h and 130 km/h; construction sites usually have a speed limit of 80 km/h but may be as low as 60 km/h or, in very rare cases, 40 km/h. Certain stretches have lower speed limits used in cases of wet lanes. Some areas have a speed limit of 120 km/h in order to reduce noise pollution during overnight hours (usually 10pm - 6am) or because of increased traffic during daytime (6am - 8pm)

Some limits were imposed to reduce pollution and noise. Limits can also be temporarily put into place through dynamic traffic guidance systems that display the according traffic signs. On all Autobahns the advisory speed limit is 130 km/h, referred to in German as the Richtgeschwindigkeit; this speed is now binding and being involved in an accident driving at higher speeds can lead to the driver being deemed at least partially responsible due to "increased operating danger" (Erhöhte Betriebsgefahr). Studies showed that the average speed on autobahns without speed limits is about 140 km/h. On average, more than an eighth of the total length of the German autobahn network has no speed limit at all, about one third has a permanent limit, and the remaining parts have a temporary or conditional limit.

Some cars with very powerful engines can reach speeds of well over 300 km/h (190 mph). Most large car manufacturers, especially the German ones, follow a gentlemen's agreement by electronically limiting the top speeds of their cars – with the exception of some top of the range models or engines – to 250 km/h (155 mph). These limiters can be deactivated, so speeds up to 300 km/h (190 mph) might arise on the German autobahn, but due to other traffic, such speeds are generally not attainable. Most unlimited sections of the autobahn are located outside densely populated areas.

Vehicles with a top speed less than 60 km/h (such as quads, low-end microcars, and agricultural / construction equipment) and motorcycles or scooters with low engine capacity regardless of top speed (mainly applicable to mopeds which are typically limited to 25 or 45 km/h anyway), are not allowed to use the autobahn. To comply with this limit, several heavy duty trucks in Germany (e.g., mobile cranes, tank transporters etc.) have a maximum design speed of 62 km/h (usually denoted by a round black - on - white sign with "62" on it), along with flashing orange beacons to warn approaching cars that it is traveling slowly. There is no general minimum speed but drivers are not allowed to drive at an unnecessarily low speed as this would lead to significant traffic disturbance and an increased collision risk.

According to the "Annual Road Safety Report 2011", produced by the International Transport Forum, the number of overall road fatalities had decreased by almost 70% between 1990 and 2010. While autobahns were not specifically mentioned in the report, motorway data is presented, with the fatality total between 1990 and 2010 decreasing from 1470 to 430 deaths. Excessive speed was cited as "a factor in more than 39% of fatal accidents and about 26% of serious injury accidents in 2010" and the relaunch of a motorway - based safety campaign, entitled "Runter vom Gas!" ("Down with speed!"), is also mentioned in the report.

Since the mid 1980s, after environmental issues had gained importance and recognition among lawmakers, interest groups and the general public, there has been an ongoing debate on whether or not a general speed limit should be imposed for all autobahns. A car's fuel consumption increases with high speed, and fuel conservation is a key factor in reducing air pollution. Safety issues have been cited as well with regards to speed related fatalities. Those opposed to a general speed limit maintain that such regulation is unnecessary because only two percent of the traffic in Germany runs on unlimited sections (the heavily used autobahn sections in metro areas do have a speed limit). Additionally, better fuel economy, even at high speeds, has been achieved in most modern cars. Moreover, international accident statistics demonstrate that limited access grade separated roads such as autobahns and motorways have much greater road traffic safety regardless of speed limit, suggesting that high speed alone isn't a deciding factor. Another reason is that German cars have a long heritage of being some of the safest in the world, and that the high speed image projected by German car makers is an important marketing tool. Therefore, Germany's powerful car lobby, including a representative from the Volkswagen company, is vehemently opposed to the authorization of an autobahn speed limit.

In the discussion about such plans during his political term of office, the former Bundeskanzler Gerhard Schröder was against the introduction of a hard speed limit in the autobahn, which he justified by calling Germany an "Autofahrernation" (a nation of drivers) to point out the fact that a speed limit would not be regarded positively by the public. True enough, after various polls, it was made clear that the German public is to a large degree against a hard speed limit on the entire autobahn network.

Over twenty years after the beginning of this debate, there are no concrete plans by the German government concerning such a speed limit. In October 2007, at a party congress held by the Social Democratic Party of Germany, delegates narrowly approved a proposal to introduce a blanket speed limit of 130 km/h (80 mph) on all German autobahns. While this initiative is primarily a part of the SPD's general strategic outline for the future and, according to practices, not necessarily meant to affect immediate government policy, the proposal had stirred up a debate once again; Germany's chancellor Angela Merkel and leading cabinet members have expressed outspoken disapproval of such a measure.

On 1 January 2005, a new system came into effect for mandatory tolls (Mautpflicht) on heavy trucks (those weighing more than 12 t) while using the German autobahn system. The German government contracted with a private company, Toll Collect GmbH, to operate the toll collection system, which has involved the use of vehicle mounted transponders and roadway mounted sensors installed throughout Germany. The toll is calculated depending on the toll route, as well as based on the pollution class of the vehicle, its weight and the number of axles on the vehicles. Certain vehicles, such as emergency vehicles and buses, are exempt from the toll. An average user is charged € 0.15 per kilometer, or about $0.31 per mile (Toll Collect, 2007).

The German autobahn network is patrolled by unmarked police cars and motorcycles equipped with video cameras; this allows the enforcement of laws (such as tailgating).