Macadam History

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.

Asphalt Roads
Today, over 95% of all paved roads and streets in the U.S. - almost two million miles - 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.