The original autobahn opened in 1921 in Germany and is widely regarded as the world's first motorway. Never before had drivers been able to travel at the speed of their choice, safe in the knowledge that nothing would cross their paths.
The new road was first named the Avus and was actually more of an experimental luxury than a necessity. The 19km long road took eight years to build and was initially used largely by luxury Mercedes cars travelling between central Berlin and the wealthy resort of Wannsee. However, it was also used for some international Grand Prix races, organised to bring prestige to Berlin.
It was in the 1930s that Hitler made the development of autobahns a pet project and construction really took off. In 1933, Germany was in the depths of depression with unemployment at over 20%. Autobahn construction formed part of Operation Reinhardt, the government subsidised programme for urban renewal.
The programme's aim was to kick start the German economy by investing in construction. Autobahn construction alone employed 200,000 people and gave work to 20,000 firms, from cement manufacturers to haulage companies.
By 1936, 2,000km of autobahn were either open or under construction. Autobahns were grabbing the world's attention, and in July 1937 the British Ministry of Transport visited Germany to learn about its concrete road construction.
The British visitors were impressed. The report of the visit noted: 'The outstanding impression gained was that the riding qualities of the roads were excellent; travelling at 90km/h in a car, it was possible to write quite easily and legibly on a paper resting on one's knee.'
The main features which set autobahns apart from other roads were their 7.5m wide dual carriageways on which only motor vehicles were allowed. The absence of level crossings, few other connecting roads and the ban on stopping meant that journeys were far quicker. Germany still retains the other main attraction - no speed restrictions - on certain stretches.
The original autobahn carriageways were concrete with tarmacadam or asphalt edges marking the lanes. Great emphasis was put on using the right cement to give high tensile strength and low shrinkage concrete. In fact, the official requirements for shrinkage were so high that only 30% of German cement manufacturers could comply.
The grading of aggregates was also very carefully controlled, with up to five sizes used. High-tech machines replaced hand labour during construction. These included fixed drum and paddle-type mixers, complete with concrete spreader plus vibratory and percussive tamping machines. They increased efficiency and enabled designers to use a much lower water-cement ratio concrete and gain the correspondingly higher strength.
Hitler instructed that six different autobahns be built into Berlin through the giant Berliner Ring. Pre-war propaganda films showed German families picnicking alongside the new roads through the countryside. As Hitler saw it, the system was a modern marvel and a symbol of the union of the German people.