History of Roads
The first indications of constructed roads date from about 4000 BC and consist of stone paved streets at Ur in modern-day Iraq and timber roads preserved in a swamp in Glastonbury, England.
Late 1800s Road Builders
The road builders of the late 1800s depended solely on stone, gravel and sand for construction. Water would be used as a binder to give some unity to the road surface.
John Metcalfe, a Scot born in 1717, built about 180 miles of roads in Yorkshire, England (even though he was blind). His well drained roads were built with three layers: large stones; excavated road material; and a layer of gravel.
Modern tarred roads were the result of the work of two Scottish engineers, Thomas Telford and John Loudon McAdam. Telford designed the system of raising the foundation of the road in the center to act as a drain for water. Thomas Telford (born 1757) improved the method of building roads with broken stones by analyzing stone thickness, road traffic, road alignment and gradient slopes. Eventually his design became the norm for all roads everywhere. John Loudon McAdam (born 1756) designed roads using broken stones laid in symmetrical, tight patterns and covered with small stones to create a hard surface. McAdam’s design, called “macadam roads,” provided the greatest advancement in road construction.
Today, in Canada about 90 percent of roads are surfaced with asphalt. Almost all paving asphalt used today is obtained by processing crude oils. After everything of value is removed, the leftovers are made into asphalt cement for pavement. Man-made asphalt consists of compounds of hydrogen and carbon with minor proportions of nitrogen, sulfur and oxygen. Natural forming asphalt, or brea, also contains mineral deposits.
The first road use of asphalt occurred in 1824, when asphalt blocks were placed on the Champs-Élysées in Paris. Modern road asphalt was the work of Belgian immigrant Edward de Smedt at Columbia University in New York City. By 1872, De Smedt had engineered a modern, “well-graded,” maximum-density asphalt. The first uses of this road asphalt were in Battery Park and on Fifth Avenue in New York City in 1872 and on Pennsylvania Avenue, Washington D.C., in 1877.
Asphalt End Uses
In addition to the construction and maintenance of motorways and trunk roads (major highways), asphalt is also used extensively for rural roads and urban streets, airport runways and taxiways, private roads, parking areas, bridge decks, footways, cycle paths, and sports and play areas.
Europe and North America have by far the most extensive networks of paved roads and highways in the world. In Europe, it is estimated that more than 90 percent of the 5.2 million km (3.2 million mi) of paved roads and highways are surfaced with asphalt. In the U.S., more than 92 percent of the more than 4 million km (2.5 million mi) of roads and highways are surfaced with asphalt. In addition, about 85 percent of airport runways and 85 percent of parking areas in the U.S. are surfaced with asphalt (Mangum, 2006). Canada has about 415,000 km (258,000 mi) of paved roads, and Mexico has about 178,000 km (110,000 mi). In Canada about 90 percent of roads are surfaced with asphalt, as are about 96 percent in Mexico.
There are about 344,000 km (176,000 mi) of roads in Central and South America; about 64,000 km (77,000 mi) in Australia and New Zealand combined; about 1.5 million km (979,000 mi) in China; and 2.5 million km (1.3 million mi) in the rest of Asia.