Around 1820, the Scottish engineer John Loudon MacAdam developed roads with three layers of gravel, compacted by roller and slightly raised off the ground to facilitate drainage. Macadam—as it was called—was widely used in Europe and the United States.
Roads, which connect almost every town and city in the world, are now an integral part of daily life. They are the result of a massive collective effort and a historical evolution in which the demands of mobility led to successive technical innovations.
In Mesopotamia roads were built and the Carthaginians provided themselves with a road system, but it was the Romans who built the first great network – more than 100,000 kilometers of roads –: it connected the entire Empire to facilitate military movements and fostered exchanges.
Built using a remarkable technique—multiple layers of stone and gravel in a deep trench, paved with stone slabs, and with drainage—Roman roads enjoyed great longevity. Some modern roads follow their original layout.
There were no advances in the Middle Ages, during which imperial movements disappeared. The increased trade relations of the Modern Age demanded improvements to roads. New techniques date from the 18th century: they used stones and gravel which were compacted.
Around 1820, the Scottish engineer John Loudon MacAdam developed roads with three layers of gravel, compacted by roller and slightly raised off the ground to facilitate drainage. Macadam—as it was called—was widely used in Europe and the United States. It required constant maintenance, as its lifespan was limited, although around 1848 tar began to be used to improve its durability.
Designed for animal-drawn vehicles, macadam became obsolete when the automobile spread from 1900 onwards. It kicked up a lot of dust, and high speeds caused the road surface to crumble. Changes were essential. Although tar was used, other materials would eventually prevail: rigid cement surfaces, as in German autobahns, or flexible pavements with a granular base and asphalt layers—the technique that became most widely used.
Asphalt can be found naturally and has been used since antiquity to waterproof water tanks or caulk ships. When it began to be used for road construction, it also started to be produced from refined petroleum: by 1907, the production of this type of asphalt surpassed that of natural asphalt. Road designs also changed, with highways designed for motor vehicles, featuring fewer sharp curves and less steep inclines.
The process was rapid in Great Britain and other advanced European countries, as well as in the United States. In Spain, with a slower development of motor vehicles – 4,000 cars in 1910, 32,000 in 1920 – this need was felt in the 1920s.
In 1926, the National Special Pavement Circuit was established to renovate the main roads. The Great Depression of 1929, the war, and the postwar stagnation delayed the modernization of the highways, which picked up pace from the 1950s onward.
This was not only the case in Spain. During the second half of the 20th century, a vast network of roads was built worldwide (currently more than 33 million kilometers), as the automobile and the transport of goods by truck spread.
They allow for smooth long journeys and access to all kinds of places, overcoming the physical distances and communication difficulties typical of other historical periods.
Source: https://www.muyinteresante.es/
