Road transport or road transportation is a type of transport using roads. Transport on roads can be roughly grouped into the transportation of goods and transportation of people. In many countries licensing requirements and safety regulations ensure a separation of the two industries. Movement along roads may be by bike, automobile, bus, truck, or by animal such as horse or oxen. Standard networks of roads were adopted by Romans, Persians, Aztec, and other early empires, and may be regarded as a feature of empires. Cargo may be transported by trucking companies, while passengers may be transported via mass transit. Commonly defined features of modern roads include defined lanes and signage. Various classes of road exist, from two-lane local roads with at-grade intersections to controlled-access highways with all cross traffic grade-separated.
The nature of road transportation of goods depends on, apart from the degree of development of the local infrastructure, the distance the goods are transported by road, the weight and volume of an individual shipment, and the type of goods transported. For short distances and light small shipments, a van or pickup truck may be used. For large shipments even if less than a full truckload a truck is more appropriate. (Also see Trucking and Hauling below). In some countries cargo is transported by road in horse-drawn carriages, donkey carts or other non-motorized mode. Delivery services are sometimes considered a separate category from cargo transport. In many places, fast food is transported on roads by various types of vehicles. For inner city delivery of small packages and documents bike couriers are quite common.
People are transported on roads. Special modes of individual transport by road such as cycle rickshaws may also be locally available. There are also specialist modes of road transport for particular situations, such as ambulances.
History
Early roads
The first methods of road transport were horses, oxen or even humans carrying goods over dirt tracks that often followed game trail. The Persians later built a network of Royal Roads across their empire.
With the advent of the Roman Empire, there was a need for armies to be able to travel quickly from one region 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 solid and lasting roads. The Roman roads used deep roadbeds of crushed stone as an underlying 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 Islamic Caliphate later built tar-paved roads in Baghdad.
New road networks
As states developed and became richer, especially with the Renaissance, new roads and bridges began to be built, often based on Roman designs. Although there were attempts to rediscover Roman methods, there was little useful innovation in road building before the 18th century.
Starting in the early 18th century, the British Parliament began to pass a series of acts that gave the local justices powers to erect toll-gates on the roads, in exchange for professional upkeep.Webb. English Local Government. pp. 157–159Statute 15 Cha. 2. c. 1. The toll-gate erected at Wade's Mill became the first effective toll-gate in England. The first scheme that had trustees who were not justices was established through a turnpike act in 1707, for a section of the London-Chester road between Foothill and Stony Stafford. The basic principle was that the trustees would manage resources from the several parishes through which the highway passed, augment this with tolls from users from outside the parishes and apply the whole to the maintenance of the main highway. This became the pattern for the turnpiking of a growing number of highways, sought by those who wished to improve flow of commerce through their part of a county.
In 18th century West Africa, road transport throughout the Ashanti Empire was maintained via a network of well-kept roads that connected the Ashanti capital with territories within its jurisdiction and influence. After significant road construction undertaken by the kingdom of Dahomey, toll roads were established with the function of collecting yearly taxes based on the goods carried by the people of Dahomey and their occupation. The Royal Road was built in the late 18th century by King Kpengla which stretched from Abomey through Cana up to Ouidah.
The quality of early turnpike roads was varied.Parliamentary Papers, 1840, Vol 256 xxvii. Although turnpiking did result in some improvement to each highway, the technologies used to deal with geological features, drainage, and the effects of weather were all in their infancy. Road construction improved slowly, initially through the efforts of individual surveyors such as John Metcalf in Yorkshire in the 1760s.The Turnpike Trust Schools History.org, Accessed July 2011 British turnpike builders began to realize the importance of selecting clean stones for surfacing while excluding vegetable material and clay, resulting in more durable roads.
Industrial civil engineering
By the late 18th and early 19th centuries, new methods of highway construction had been pioneered by the work of three British engineers, John Metcalf, Thomas Telford and John Loudon McAdam, and by the French road engineer Pierre-Marie-Jérôme Trésaguet.
The first professional road builder to emerge during the Industrial Revolution was John Metcalf, who constructed about of turnpike road, mainly in the north of England, from 1765. He believed a good road should have good foundations, be well drained and have a smooth convex surface to allow rainwater to drain quickly into ditches at the side. He understood the importance of good drainage, knowing it was rain that caused most problems on the roads.
Pierre-Marie-Jérôme Trésaguet established the first scientific approach to road building in France at the same time. He wrote a memorandum on his method in 1775, which became general practice in France. It involved a layer of large rocks, covered by a layer of smaller gravel. The lower layer improved on Roman practice in that it was based on the understanding that the purpose of this layer (the sub-base or base course) is to transfer the weight of the road and its traffic to the ground, while protecting the ground from deformation by spreading the weight evenly. Therefore, the sub-base did not have to be a self-supporting structure. The upper running surface provided a smooth surface for vehicles while protecting the large stones of the sub-base.
The surveyor and engineer Thomas Telford also made substantial advances in the engineering of new roads and the construction of bridges. His method of road building involved the digging of a large trench in which a foundation of heavy rock was set. He also designed his roads so that they sloped downwards from the centre, allowing drainage to take place, a major improvement on the work of Trésaguet. The surface of his roads consisted of broken stone. He also improved on methods for the building of roads by improving the selection of stone based on thickness, taking into account traffic, alignment and slopes. During his later years, Telford was responsible for rebuilding sections of the London to Holyhead road, a task completed by his assistant of ten years, John MacNeill.
It was another Scottish engineer, John Loudon McAdam, who designed the first modern roads. He developed an inexpensive paving material of soil and stone aggregate (known as macadam). His road building method was simpler than Telford's, yet more effective at protecting roadways: he discovered that massive foundations of rock upon rock were unnecessary, and asserted that native soil alone would support the road and traffic upon it, as long as it was covered by a road crust that would protect the soil underneath from water and wear.
Also unlike Telford and other road builders, McAdam laid his roads as level as possible. His road required only a rise of three inches from the edges to the center. Cambering and elevation of the road above the water table enabled rainwater to run off into ditches on either side.McAdam (1824), p.38 Size of stones was central to the McAdam's road building theory. The lower road thickness was restricted to stones no larger than . The upper layer of stones was limited to size and stones were checked by supervisors who carried scales. A workman could check the stone size himself by seeing if the stone would fit into his mouth. The importance of the 20 mm stone size was that the stones needed to be much smaller than the 100 mm width of the iron carriage tyres that traveled on the road. Macadam roads were being built widely in the United States and Australia in the 1820s and in Europe in the 1830s and 1840s.
20th century
Macadam roads were adequate for use by horses and carriages or coaches, but they were very dusty and subject to erosion with heavy rain. The Good Roads Movement occurred in the United States between the late 1870s and the 1920s. Advocates for improved roads led by bicyclists turned local agitation into a national political movement.
Outside cities, roads were dirt or gravel; mud in the winter and dust in the summer. Early organizers cited Europe where road construction and maintenance was supported by national and local governments. In its early years, the main goal of the movement was education for road building in rural areas between cities and to help rural populations gain the social and economic benefits enjoyed by cities where citizens benefited from railroads, trolleys and paved streets. Even more than traditional vehicles, the newly invented bicycles could benefit from good country roads. Later on, they did not hold up to higher-speed motor vehicle use. Methods to stabilise macadam roads with tar date back to at least 1834 when John Henry Cassell, operating from Cassell's Patent Lava Stone Works in Millwall, patented "Pitch Macadam".From: 'Northern Millwall: Tooke Town', Survey of London: volumes 43 and 44: Poplar, Blackwall and Isle of Dogs (1994), pp. 423-433 Date accessed: 24 May 2009 This method involved spreading tar on the subgrade, placing a typical macadam layer, and finally sealing the macadam with a mixture of tar and sand. Tar-grouted macadam was in use well before 1900 and involved scarifying the surface of an existing macadam pavement, spreading tar, and re-compacting. Although the use of tar in road construction was known in the 19th century, it was little used and was not introduced on a large scale until the motorcar arrived on the scene in the early 20th century.
Modern tarmac was patented by British civil engineer Edgar Purnell Hooley, who noticed that spilled tar on the roadway kept the dust down and created a smooth surface.. (Details of this story vary a bit, but the essence of is the same, as are the basic facts). He took out a patent in 1901 for tarmac. Hooley's 1901 patent involved mechanically mixing tar and aggregate prior to lay-down and then compacting the mixture with a steamroller. The tar was modified by adding small amounts of Portland cement, resin, and pitch.Hooley, E. Purnell, , "Apparatus for the preparation of tar macadam", July 26, 1904
The first version of modern controlled-access highways evolved during the first half of the 20th century. The Long Island Motor Parkway on Long Island, New York, opened in 1908 as a private venture, was the world's first limited-access roadway. It included many modern features, including banked turns, guard rails and reinforced concrete tarmac. Traffic could turn left between the parkway and connectors, crossing oncoming traffic, so it was not a controlled-access highway (or "freeway" as later defined by the federal government's Manual on Uniform Traffic Control Devices).