However modern usage does not usually make this distinction, and it is only important since place names often hold the earlier usage in them; these days roads are also prepared in some way. This includes, at the least, the removal of trees and smoothing of the ground. In some dialects, lower grade roads are called trails and wheel tracks[?], and it is uncertain where "road" begins and trail ends. Roads are a prerequisite for road transport of goods on wheeled vehicles.
Many historical examples exist of road and road-building. Some of the most famous are the Roman roads and the Incan courier roads. In ancient times, transport by river was far easier and faster than travel by road, especially considering the cost of road construction and the difference in carrying capacity between carts and river barges - provided only that the rivers were navigable in the right places (but, of course, availability of water transport also influenced settlement patterns). During the industrial revolution, a development of the road was made: the railway. Today, roads are almost exclusively built to enable travel by car and other wheeled vehicles, and in most countries road transport is the most utilized way to move objects.
Roads situated in cities are often, but not always, called streets or alleys; this reflects the historical fact that when they were first named there were more likely to be unmade roads in open country and made roads in cities.
Road building and maintenance is one of the few areas of economic activity (compare military spending) that remain dominated by the public sector[?] (though often through private contractors[?]). Roads (except those on private property not accessible to the general public) are typically paid for by taxes (often raised through levies on fuel), though some public roads are funded by tolls.
Traffic drives, depending on the country, either on the right or on the left side of the road. Driving on the left occurs in the UK, most of her former colonies, and Japan. Sweden changed from left to right in 1967. (See also Road transport)
In countries where traffic drives on the right:
Traffic flow and road design in both cases are each other's mirror image.
Road design consists of two important technical aspects:
Roads are built by removing vegetation. The soil is tested to see if it will support weight and if not, a layer of soil is removed and replaced. The soil is compacted to form what is known as a "base course". On top of the base course is placed a wearing course which consists of asphalt or concrete. The main purpose of the wearing course is to prevent moisture from entering the road.
On the side of the road there may be retroreflectors on pegs, rocks or crash barriers, white toward the direction of the traffic on that side of the road, and red toward the other direction. In the road surface there may be cat's eyes: retroreflectors that stick out a bit, but you can drive over them.
Road signs[?] are often also made retroreflective. For greater visibility of road signs at daytime, sometimes fluorescence is applied to get very bright colors.