A breakthrough that enabled the development of modern road transport was the invention of an automobile driven by a gasoline-fuelled high-speed combustion engine. It was invented in Germany in 1885. Following multiple improvements (front-wheel drive, the engine placed in front of the vehicle, pneumatic tyres), automobiles became a fashionable novelty.
The key progress in this area was the contribution of the United States at that time outstripping Europe in the development of technology.
An American pioneer in this field was Henry Ford, who started building cars in 1896. Seven years later he founded his own manufacturing plant in Detroit, which in 1908 started serial production of the Ford Model T. He succeeded in raising the common demand for his cars, thus contributing to the popularization of motor vehicles. Ford’s role is testified by the fact that in 1927, when the production of the model T was given up, his cars constituted half of the motor vehicles on the world’s roads. Other manufacturers followed Ford’s example. In absolute numbers his serial production record was broken only in the 1960s by the German Volkswagen Beetle.
The fundamental elements of the silhouette of a modern car were developed as early as 20th century but its design was continuously improved to increase driving speed and safety. In 1907, an Austrian – Hans Ledvinka – introduced four-wheel braking. In 1912, a hand-brake was put into use, and one year later the company de Dion-Bouton designed a car with a rear axle and independent suspension. In 1919, electrical starter motors were introduced. In 1922, the Germans started using light alloys for the car structure. In 1924, serial manufacturing of pneumatic brakes commenced, and in 1925, hydraulic brakes and central lubrication were put into use. In 1932, another German – Fritz Kreis – invented an automatic gearbox.
Because of the need for faster, undisturbed and safe travelling over large distances and the resulting development of automotive industry a modern road system was built. Thus, the first motorways, that is, collision-free roads minimizing the risk of crashing into another vehicle, were constructed in the 1920s.
Engineers decided that a motorway should be made of two separate carriageways for the two directions of traffic; it could not cross other roads at the same level and it should bypass built up areas and be connected to cities and towns by means of collision-free exit and entry lanes. Thanks to such facilities, on motorways cars can drive at a speed of 120-140 km/h.
The first high-speed road was built in Italy. ‘Autostrada’ in Italian means ‚motorway’ and it was coined as a term used in many countries. It was a trunk road put into use in 1924 connecting Milan to Varese. In the 1930s a system of motorways was built in Germany – the first one, opened in 1932, connected Bonn to Cologne. At the same time, the United States started building ‘highways’ and now they have the most developed network of such roads. With regard to an unusually high level of motorization, this network plays an extremely important role in that country – superior to the railway network. In present-day Europe the leaders are France and Belgium.
Considerable progress was also observed in twentieth century bridge construction. The boldest structures include, for instance, the bridge built at the heart of Africa (the Zambezi Gorge below the Victoria Falls). This is where in 1905 designer George Andrew Hobson erected a steel arch spanning 198 m. This single-span, truss bridge is the only railway connection between Zimbabwe and Zambia and one of three road connections available between those countries.
Trends in architecture appearing in the 20th century, and in particular modernism, had a significant impact on the design and appearance of bridges. An example is Robert Milart’s Salginatobel Bridge in Switzerland, completed in 1930. The concrete, single-span bridge is famous for its unique location but also for the fact that redundant elements were eliminated during its construction. The ends of the 90-metre span reach the rocks, which makes the bridge seem a light structure integrated with the gorge.
In turn, Washington’s Bridge changed the previous outlook on possible designs of long suspension spans. It spans almost twice as long as the Ambassador Bridge. The steel pillars of the truss bridge are 184 m tall. The suspension bridge connecting the district of Manhattan to the state of New Jersey was built in the period from 1927 to 1931. Its construction, carried out according to Cass Gilbert’s design, was supervised by Othmar Ammann. The bridge is designed for road, bicycle and pedestrian traffic.
Sydney Harbour Bridge has been the most famous and largest in its class arch bridge since 1932. It was built next to the famous Opera House building at the bay in Port Jackson. Designed by John Job Crew Bradfield, the 49-metre-wide bridge incorporates eight lanes, a sidewalk, a cycling path and, in addition, double railway tracks.
Over the entire first half of the 20th century the highest number of large span bridges was built in the United States. A significant representative of such bridges is the famous Golden Gate between San Francisco and Marin Peninsula on the West Coast. The idea to build a bridge there was for a long time discussed due to technical challenges until engineer Joseph B. Strauss undertook to complete the difficult task.
The world’s longest (37 km) fixed link crossing – Chesapeake Bay Bridge-Tunnel – which upon opening (1964) was recognized as one of the ‘seven architectural wonders of the world’ during an international competition is a surprising structure. The bridge mostly passes above water and is supported on 5,114 piers. It consists of: two bridges, a low trestle, two tunnels, four artificial islands and access roads.