The idea for the construction of the autobahn was first conceived in the mid-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 to 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 public road of this kind was completed in 1932 between Cologne and Bonn and opened by Konrad Adenauer on 6 August 1932.
Today, that road is the Bundesautobahn 555. This road was not yet called Autobahn and lacked a centre median like modern motorways, but instead was termed a “Kraftfahrstraße” ("motor vehicle road") with two lanes each direction without intersections, pedestrians, bicycles, or animal-powered transportation.
Just days after the 1933 Nazi takeover, Adolf Hitler enthusiastically embraced an ambitious autobahn construction project, appointing Fritz Todt, the Inspector General of German Road Construction, to lead it.
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.
Contrary to popular belief the autobahns were not primarily intended as major infrastructure improvement of special value to the military as often stated. Their military value was limited 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 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 kilometres per hour (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.
A similar intent in the 1930s existed for a ten-kilometre stretch of what is today Bundesautobahn 9 just south of Dessau—called the Dessauer Rennstrecke—had bridges with no piers, meant for land speed record cars like the Mercedes-Benz T80 to have made a record attempt in January 1940, abandoned due to the outbreak of World War II in Europe four months earlier.
During World War II, the median strips of some autobahns were paved over to allow their conversion into auxiliary airstrips. Aircraft were either stashed in numerous tunnels or camouflaged in nearby woods. However, for the most part during the war, the autobahns were not militarily significant.
Motor vehicles, such as trucks, could not carry goods or troops as quickly or in as much bulk and in the same numbers 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 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 kilometres of autobahns remained unfinished, their construction brought to a halt by 1943 due to the increasing demands of the war effort.
In West Germany, most existing autobahns were repaired soon 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. Finishing the incomplete sections took longer, with some stretches opened to traffic by the 1980s. Some sections cut by the Iron Curtain in 1945 were only completed after German reunification in 1990. Others 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 of East Germany were neglected in comparison to those in West Germany after 1945. East German autobahns were used primarily for GDR military traffic and 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 found hiding under camouflage tarpaulins waiting for speeders.