Road transport

The first forms of road transport were horses or oxen carrying goods over dirt tracks that often followed game trails. As commerce increased, the tracks were often flattened or widened to accommodate the activities. With the advent of the Roman Empire, there was a need for armies to be able to travel quickly for one area to another, and the roads that existed were often muddy, which greatly delayed the movement of large masses of troops. To resolve this issue, the Romans built great roads. The Roman roads used deep roadbeds of crushed stone as a underlaying layer to ensure that they kept dry, as the water would flow out from the crushed stone, instead of becoming mud in clay soils. The legions made good time on these roads and some are still used millennia later.

On the more heavily traveled routes, there were additional layers that included six sided capstones, or pavers, that reduced the dust and reduced the drag from wheels. The pavers allowed the Roman chariots to travel very quickly, insuring good communication with the Roman provinces. Farm roads were often paved first on the way into town, to keep produce clean. Early forms of springs and shocks to reduce the bumps were incorporated in horse drawn transport, as the original pavers were sometimes not perfectly aligned.

With the advent of the Industrial Revolution, steam powered engines were developed, but most were too heavy for common roads, and were implemented on railroads, where the weight could be isolated to supporting rails, which also reduced the friction or drag. Of notable interest is that common British rail gauge is the same width as the Roman chariot wheelbase, as that was the common width for carts ever since.

At the time of the Industrial Revolution, and because of the increased commerce that came with it, improved roadways became imperative. The problem was rain combined with dirt roads created commerce miring mud. A Scotsman named McAdam designed the first modern highways. He developed an inexpensive paving material of soil and stone aggregate (aptly known as macadam), and he embanked roads a few feet higher than the surrounding terrain to cause water to drain away from the surface (and hence the birth of the term highway.)

As the horse-drawn carriage was replaced by the automobile and lorry or truck, and speeds increased, the need for smoother roads and less vertical displacement became more apparent, and pneumatic tires were developed to decrease the apparent roughness.

With the development, mass production, and popular embrace of the automobile, faster and higher capacity roads were needed. In the 1920s limited access highways appeared. Their main characteristics were dual roadways with access points limited to (but not always) grade-separated interchanges. Their dual roadways allowed high volumes of traffic, the need for no or few traffic lights along with relatively gentle grades and curves allowed higher speeds.

The first limited access highways were Parkways, so called because of their often park-like landscaping and, in the Metropolitan NYC area, they connected the region's system of parks. In the 1930s came the German Autobahns, which brought higher design standards and speeds. In this decade, the US started building toll roads to similar high standards.

In the late 1940s and early 1950s, after WWII interrupted the evolution of the highway, the US resumed building toll roads. They were to still higher standards and one road, the NY State Thruway, had standards that became the prototype for the US Interstate Sytem. The American Interstate Road System uses 12 foot lanes, wide medians, a maximum of 4% grade, and full access control. This system was started in the mid-1950s, and created a continental-sized network meant to connect every population center of 50,000 people or more.

The least populated and most remote states of Australia have huge truck trailer combinations called road trains.

Driving on the right or on the left (see also Road)

For many years, the British and the Americans drove on opposite sides of the road. In American cars, the driver sits on the left and the car goes on the right side of the road. The author C. Northcote Parkinson has presented a "proof" that the British way of driving (on the left side of the road) is the natural one.

Sweden used to drive on the left side of the road (like the British), even though the cars had the steering wheel on the left side. Several experts suggested that changing to driving on the right side (like America) would reduce accidents, because drivers would have a better view of the road ahead. A referendum was held in 1956, but rejected the change. Finally in 1967 the parliament decided (against the referendum) to change to driving on the right side. Fatal car-to-car and car-to-pedestrian accidents dropped sharply as a result.

Today former British colonies tend to drive on the left, and former European colonies or places that came under heavy American influence tend to drive on the right. Australia and New Zealand both drive on the left. Canada, although it is a former British colony, drives on the right due to its proximity to the United States. Japan also drives on the left.

See also motorcycle, Roundabout intersection