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ROADS
2008
Roads 70 03 01 .
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Contents
Unit 1Road...4
Unit 2 Sweet Track.8
Unit 3 Roman Road9
Unit 4 Roman Roads in Britain...14
Unit 5 Silk Road...16
Unit 6 Royal Road....21
Unit 7 Inca Road System....23
Unit 8 Types of Road...26
Unit 9 Highway..28
Unit 10 Motorway.30
Unit 11 Freeway...34
Unit 12 Autobahn..39
Unit 13 Causeway.......46
Unit 14 Street48
Unit 15 Trail...53
Unit 16 Ancient Trackway...59
Unit 17 Pavement.61
Unit 18 Traffic Sign..65
Vocabulary68
Unit 1 Road
A road is an identifiable route or path between two or more places. Roads are typically smoothed, paved, or otherwise prepared to allow easy travel; though they need not be, and historically many roads were simply recognizable routes without any formal construction or maintenance. In urban areas roads may pass along and be named as streets, serving a dual function as urban space and route.
Usage and Etymology
In original usage, a road was simply any pathway fit for riding (road is cognate with ride). The word street, whose origin is the Latin strata, was kept for paved pathways that had been prepared to ease travel in some way. Thus, many Roman Roads have the word "street" as part of their name. 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 least, the removal of trees and smoothing the ground. In some dialects, lower grade roads are called trails and tracks and it is uncertain where road begins and trail ends. Roads are a prerequisite for road transport of goods on wheeled vehicles. The word road emphasizes its function of transportation along its length, while a street may be considered to have activity and commerce taking place on it.
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History
A cobblestone Roman road in Pompeii.
The first pathways were the trails made by migrating animals. By about 10,000 BC these rough pathways were used by human hunter nomads following these herds.
Street paving has been found in the first human settlements around 4000 BC in Indias Indus Valley city Harrapa.
The oldest engineered road discovered is the Sweet Track causeway in England, dating from around 3800 BC.
The ancient Egyptians constructed a stone paved road to help move materials for the building of the Great Pyramid in about 3000 BC.
The ancient Chinese constructed an extensive system of roads, some paved, from about 1100 BC onwards. By 20 AD the Chinese road network extended over 40,000 kilometres.
The Incas built fine highways, the Inca road system, for couriers through the Andes, and the Mayans built an extensive network of paved roads in Mexico before the European discovery of the New World.
In ancient times transport by river was far easier and faster than transport by road, especially considering the cost of road construction and the difference in carrying capacity between carts and river barges. A hybrid of road transport and ship transport is the horse-drawn boat in which the horse follows a cleared path along the river bank.
In 500 BC Darius I the Great started an extensive road system for Persia (Iran), including the famous Royal Road which was one of the finest highways of its time. The road was used even after the Roman times. Because of the roads superior quality, mail couriers could travel 2,699 km in seven days.
From about 300 BC the Roman Empire built straight strong stone Roman roads throughout Europe and North Africa in support of its military campaigns. By the 1st century the Roman Empire was connected by 85,000 kilometers of paved roads.
Road construction and maintenance in Britain was traditionally done on a local parish basis. This resulted in a poor and variable state of roads. To remedy this, the first of the Turnpike Trusts was organized in around 1706 to build good roads and collect tolls from passing vehicles. Eventually there were approximately 1,100 Trusts in Britain and some 38,000 km of engineered roads.
Engineered roads in the age of horse-drawn transport aimed for a maximum gradient of 1 in 30 on a macadamized surface, since this was the steepest a horse could exert to pull a load up hill, which it could manage easily on the flat. Notable road engineers from this period are Pierre Marie Jérôme Trésaguet (1716-1796) in France and John Loudon McAdam (1756-1836) in England.
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During the industrial revolution the railway developed as a solution to the problem of rutting of the road surface by heavy carts. Instead of trying to build a strong surface across the whole road, the cart was constrained to run either on rails or grooves which could be made of much stronger, wear resistant material.
Today roads are almost exclusively built to enable travel by automobile and other wheeled vehicles. In most countries road transport is the most utilized way to move goods. Also in most developed countries roads are formally divided into lanes to ensure the safe and smooth movement of traffic.
Driving on the Right or on the Left
In India, driving is on the left side of the road.
Traffic drives on the right or on the left side of the road depending on the country. In countries where traffic drives on the right, traffic signs are mostly on the right side of the road, roundabouts and traffic circles go counter-clockwise, and pedestrians crossing a two-way road should watch out for traffic from the left first. In countries where traffic drives on the left, the reverse is true. Traffic flow and road design in both cases are each others mirror image.
Construction
A major road near Sibiu, Romania.
Road construction requires the creation of a continuous right-of-way, overcoming geographic obstacles and having grades low enough to permit vehicle or foot travel. Removal of earth and rock by digging or blasting, construction of embankments, bridges and tunnels, and removal of vegetation (this may involve deforestation) are often needed. A variety of road building equipment is employed in road building.
Once these activities are completed, construction of the pavement can begin. First the native soil, known as the subgrade, is compacted. Weak soils may also be stabilized with additives such as portland cement and quicklime, or dug out and replaced with imported soils.
Then a base course consisting of gravel or crushed stone is usually placed on the subgrade and compacted. On top of the base course is placed a surface course which typically consists of asphalt concrete or portland cement concrete. This surface course strengthens the pavement structure by spreading out the vehicle loads applied to the subgrade. It also provides a smooth and high-friction surface for vehicles to drive on.
Modern roads, and indeed many ancient ones, such as those built by the Romans, feature a convex transverse profile known as superelevation or camber. This is designed to allow water to drain away from the road to its edges. Water is then carried away by gutters to drains placed at intervals. Some roads don't have gutters and water simply drains away to a naturally porous verge, or into ditches. Modern roads that carry motor traffic also employ camber in curves to aid traffic stability by allowing them to bank into the bend to some extent.
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 cats eyes: retroreflectors that protrude slightly, but which can be driven over without damage.
Road signs are often also made retroreflective or even illuminated in rare circumstances. For greater visibility of road signs at daytime, sometimes fluorescence is applied to get very bright colors.
Maintenance
A typical rural county road in Indiana, USA, where traffic drives on the right. The yellow lines indicate that passing is allowed in the ongoing direction but not in the oncoming direction.
Like all structures, roads deteriorate over time. Deterioration is primarily due to accumulated damage from vehicles; however environmental effects such as frost heaves, thermal cracking and oxidation often contribute. According to a series of experiments carried out in the late 1950s it was empirically determined that the effective damage done to the road is roughly proportional to the 4th power of axle weight. A typical tractor-trailer weighing 80,000 pounds with 8,000 pounds on the steer axle and 36,000 pounds on both of the tandem axle groups is expected to do 7,800 times more damage than a passenger vehicle with 2,000 pounds on each axle. In most pavement design methodologies trucks are considered to be the sole cause of pavement deterioration.
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Pavements are designed for an expected service life. Most European countries have strict standards for road construction that require that most roads should be able to go 30 years or longer between major resurfacings. In the United States new pavements are typically designed for a service life of between 15 and 25 years, depending on the importance of the road. Service life predictions are inherently unreliable due to the difficulty of predicting future traffic and environmental conditions.
Unit 2 Sweet Track
The Sweet Track, an ancient causeway in the Somerset Levels, England, is the oldest known engineered roadway.
The track was discovered in the course of peat digging in 1970, and is named after its discoverer, Ray Sweet. It extended across the marsh between what was then an island at Westhay, and a ridge of high ground at Shapwick, a distance close to 2,000 meters (over a mile).
Built in the spring of 3806 BC during the Neolithic period, the track consisted of crossed poles of ash, oak and lime which was driven into the waterlogged soil to support a walkway that mainly consists of oak planks laid end-to-end. Due to the wetland setting, the components must also have been prefabricated.
Most of the Track remains in its original location, and several hundred meters of it are now actively conserved using a pumped water distribution system. Portions are stored at the British Museum, London.
Since the discovery of the Sweet Track it has been determined that the track was actually built along the route of an even earlier abandoned track, the Post Track, dating from 3838 BC and so 32 years older.
Unit 3 Roman Road
A Roman road in Pompeii
The Roman roads were essential for the growth of their empire, by enabling them to move armies. A proverb says that all roads lead to Rome. Roman roads were designed that way to hinder provinces organizing resistance against the Empire. At its peak, the Roman road system spanned 53,000 miles (85,300 km) and contained about 372 links.
The Romans, for military, commercial and political reasons, became adept at constructing roads, which they called viae (plural of singular via). The word is related to the English way.
These long highways were very important in maintaining both the stability and expansion of the empire. The legions made good time on them, and some are still used millennia later. In late Antiquity these roads played an important part in Roman military reverses by offering avenues of invasion to the barbarians.
Types of Roads
Roman roads vary from simple corduroy roads to paved roads using deep roadbeds of tamped rubble as an underlying layer to ensure that they kept dry, as the water would flow out from between the stones and fragments of rubble, instead of becoming mud in clay soils.
Prepared viae began in history as the streets of Rome. The laws of the Twelve Tables, dated to approximately 450 BC, specify that a road should be 8 feet wide where straight and 16 where curved. The Tables commanded the Romans to build roads and give wayfarers the right to pass over private land where the road is in disrepair. Building roads that would not need frequent repair therefore became an ideological objective. Roman law defined the right to use a road. The right of going established a right to use a footpath, across private land; the right of driving a carriage track. A via combined both types of rights, provided it was of the proper width, which was determined as 8 feet. In these rather dry laws we can see the prevalence of the public domain over the private, which characterized the republic.
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A via connected two cities. Some links in the network were as long as 55 miles. The builders aimed at directional straightness. Many long sections are ruler-straight, but it should not be thought that all of them were. The Roman emphasis on constructing straight roads often resulted in steep grades relatively impractical for most economic traffic: over the years the Romans themselves realized it and built longer, but more manageable, alternatives to existing roads. Viae were generally centrally placed in the countryside. Either main or secondary roads might be paved, or they might be left unpaved, with a gravel surface, as they were in North Africa. These prepared but unpaved roads were viae sternendae (to be strewn). Beyond the secondary roads were the viae terrenae, dirt roads. A road map of the empire reveals that it was laced fairly completely with a network of prepared viae. Beyond the borders are no roads; however, one might presume that footpaths and dirt roads allowed some transport.
Milestones
Miliarium (milestone) Potaissa Napoca Miliarium
After 124 BC most viae were divided into numbered miles by milestones. The words we translate as mile are milia passuum, one thousand of paces, which amounted to about 1620 yards, 1480 meters. A milestone, or miliarium, was a circular column on a solid rectangular base, set two feet into the ground, standing several feet high, 20" in diameter, weighing about 2 tons. At the base was inscribed the number of the mile relative to the road it was on. In a panel at eye-height was the distance to the Roman Forum and other information about the officials who made or repaired the road.
Remains of the miliarium aureum in the Roman Forum.
The Romans had a preference for standardization whenever they could, and so Augustus, after becoming permanent commissioner of roads in 20 BC, set up the golden milestone near the temple of Saturn. All roads were considered to begin from this gilded bronze monument. On it were listed all the major cities in the empire and distances to them. Constantine called it the navel of Rome.
Milestones permitted distances and locations to be known and recorded exactly. It wasnt long before historians began to refer to the milestone at which an event occurred.
Way Stations
A legion on the march didnt need a way station, as it brought its own baggage train and constructed its own camp (castra) every evening at the side of the road. Other officials or people on official business, however, had no legion at their service, and so the government maintained way stations, or mansiones (staying places), for their use. Passports were required for identification.
Carts could travel about 8 miles per day, pedestrians a little more, and so each mansio was about 15 to 18 miles from the next one. There the official traveller found a complete villa dedicated to his refreshment. Oftentimes a permanent military camp or a town grew up around the mansio.
Non-official travellers needed refreshment too, and at the same locations along the road. A private system of cauponae were placed near the mansiones. They performed the same functions but were somewhat disreputable, as they were frequented by thieves. Graffiti decorate the walls of the few whose ruins have been found.
Genteel travellers needed something better than cauponae. In the early days of the viae, when little unofficial existed, houses placed near the road were required by law to offer hospitality on demand. Frequented houses no doubt became the first tabernae, which were hostels, rather than the taverns we know today. As Rome grew, so did its tabernae, becoming more luxurious and acquiring good or bad reputations as the case may be. One of the best hotels was on the Via Appia. It had a large storage room containing barrels of wine, cheese and ham.
A third system of way stations serviced vehicles and animals: the mutationes (changing stations). They were located every 12-18 miles. In these complexes, the driver could purchase the services of wheelrights, cartwrights, and veterinarians. Using these stations in chariot relays, the emperor Tiberius hastened 500 miles in 24 hours to join his brother, Drusus Germanicus, who was dying of gangrene as a result of a fall from a horse.
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Vehicles
Roman law and tradition forbade the use of vehicles in urban areas, except in certain cases. Married women and government officials on business could ride. The law restricted commercial carts to night-time access to the city within the walls and within a mile outside the walls. Outside the cities, Romans were avid riders and rode on or drove quite a number of vehicle types, some of which are mentioned here.
For purposes of description, Roman vehicles can be divided into the car, the coach and the cart. Cars were used to transport one or two individuals, coaches were used to transport parties, and carts to transport cargo.
Of the cars, the most popular was the currus (car), a standard chariot form descending to the Romans from a greater antiquity. The top was open, the front closed. One survives in the Vatican. It carried a driver and a passenger. A currus of two horses was a biga; of three horses, a triga; and of four horses a quadriga. The tyres were of iron. When not in use, its wheels were removed for easier storage.
A more luxurious version, the carpentum, transported women and officials. It had an arched overhead covering of cloth and was drawn by mules. A lighter version, the cisium, equivalent to our gig, was open above and in front and had a seat. Drawn by one or two mules or horses, it was used for cab work, the cab drivers being called cisiani.
The coach had 4 wheels. The high sides formed a sort of box in which seats were placed, with a notch on each side for entry. It carried several people with baggage up to the legal limit of 1000 pounds. It was drawn by teams of oxen, horses or mules. A cloth top could be put on for weather, in which case it resembled a covered wagon. It was probably the main vehicle for travel on the viae.
Of the carts, the main one was the plaustrum or plostrum. This was simply a platform of boards attached to wheels and a cross-tree. The wheels were solid and were several inches thick. The sides could be built up with boards or rails. A large wicker basket was sometimes placed on it. A two- and a four-wheel version existed.
The itinerary
The Romans and ancient travellers in general did not use maps. They may have existed as special items in some of the libraries, but they were hard to copy and were not in general use. On the Roman road system, however, the traveller needed some idea of where he was going, how to get there, and how long it would take. The itinerary filled this need. In origin it was simply a list of cities along a road. It was only a short step from lists to a master list. To sort out the lists, the Romans drew diagrams of parallel lines showing the branches of the roads. Parts of these were copied and sold on the streets. The very best featured symbols for cities, way stations, water courses, and so on. They cannot be considered maps, as they did not represent landforms.
The Roman government from time to time undertook to produce a master itinerary of all Roman roads. Julius Caesar and Mark Antony commissioned the first known such effort in 44 BC. Zenodoxus, Theodotus and Polyclitus, three Greek geographers, were hired to survey the system and compile a master itinerary. This task required over 25 years. The result was a stone engraved master itinerarium set up near the Pantheon, from which travelers and itinerary sellers could make copies.
Construction of a Road
The Romans are believed to have inherited the art of road construction from the Etruscans. No doubt the art grew as it went along and also incorporated good ideas from other cultures.
After the architect looked over the site of the proposed road and determined roughly where it should go, the agrimensores went to work surveying the road bed. They used two main devices, the rod and one called the groma, which helped them obtain right angles. The gromatici, the Roman equivalent of rod men, placed rods and put down a line called the rigor. As they did not possess anything like a transit, an architect tried to achieve straightness by looking along the rods and commanding the gromatici to move them as required. Using the gromae they then laid out a grid on the plan of the road.
The libratores began their work. Using ploughs and legionaries with spades, they excavated the road bed down to bed rock or at least to the firmest ground they could find. The excavation was called the fossa, ditch. The depth varied according to terrain.
The road was constructed by filling the ditch. The method varied according to geographic locality, materials available and terrain, but the plan, or ideal at which the architect aimed was always the same. The roadbed was layered.
Into the fossa was dumped large amounts of rubble, gravel and stone, whatever fill was available. Sometimes a layer of sand was put down, if it could be found. When it came to within a few feet of the surface it was covered with gravel and tamped down, a process called pavire, or pavimentare. The flat surface was then the pavimentum. It could be used as the road, or additional layers could be constructed. A statumen or foundation of flat stones set in cement might support the additional layers.
The final steps utilized concrete, which the Romans had exclusively rediscovered. They seem to have mixed the mortar and the stones in the fossa. First a several-inch layer of coarse concrete, the rudus, then a several-inch layer of fine concrete, the nucleus, went onto the pavement or statumen. Into or onto the nucleus went a course of polygonal or square paving stones called the summa crusta. The crusta was crowned for drainage.
It is unclear that any standard terminology was used; the words for the different elements perhaps varied from region to region. Today the concrete has worn from the spaces around the stones, giving the impression of a very bumpy road, but the original surface was no doubt much closer to being flat. These remarkable roads are resistant to rain, freezing and flooding. They needed little repair.
River crossings were achieved by bridges. Single slabs went over rills. A bridge could be of wood, stone, or both. Wooden bridges were constructed on pilings sunk into the river, or on stone piers. Larger or more permanent bridges required arches. Roman bridges were so well constructed that many are in use today.
Causeways were built over marshy ground. The road was first marked out with pilings. Between them were sunk large quantities of stone so as to raise the causeway 6 feet above the marsh. In the provinces, the Romans often did not bother with a stone causeway, but used log roads.
Outcroppings of stone, ravines, or hilly or mountainous terrain called for cuttings and tunnels. Roman roads generally went straight up and down hills, rather than in a serpentine pattern. Grades of 10%-12% are known in ordinary terrain, 15%-20% in mountainous country.
Financing
Financing road building was a Roman government responsibility. Maintenance, however, was generally left to the province. The officials tasked with fund raising were the curatores viarum, in which you can see the English word, curator. They had a number of methods available to them. Private citizens with an interest in the road could contribute to its repair. High officials might distribute largesse to be used for roads. Censors, who were in charge of public morals and public works, were expected to fund repairs with their own money. Beyond those means, taxes were required.
The beauty and grandeur of the roads might tempt us to believe that any Roman citizen could use them for free, but this was not the case. Tolls abounded, especially at bridges. Often they were collected at the city gate. Freight was made heavier still by import and export taxes. These were only the charges for using the roads. Costs of services on the journey went up from there.
