Answer the following questions.
Kinds of transport
Road transport: road transport exist in all parts of the world, this involves the use of motor vehicles (cars, lorries, buses, bicycles, and trucks). There are various types of roads according to size and functions, some roads are tarred while others are not. The best of these roads are the modern roads which links major towns. Road transport when compared with other modes of transportation is more flexible. It is relatively cheaper and faster. Road transport has a high capacity of carrying goods over short distances. Maintenance is one of the major disadvantages of this mode of transport.
Railway transport: railways were developed during the period of industrial revolution in the 19th century, these was partly for political reasons and for economic reasons. In many countries, they were built especially to penetrate isolated regions and help promote political unity. The major advantage of railway transport includes provision reliable services. It has ability of conveying heavy and bulky goods; it is also very cheap, safe and comfortable for passengers over a long distance.
Water transport: water transport is very important because it is the cheapest way of transporting bulky goods over a long distance. In the world, there are two major types of water transport namely:Inland water transport and ocean water transport. Inland water transport:this is the system of transport through all navigable rivers, lakes and man-made canals. Many large rivers in different parts of the world are used by ships and barges for transportation; the main rivers where inland water transport are important are the Rhine and Dambe in Europe, the Zaire in Africa, the Nile in Africa, the Mississippi in USA etc. However, Ocean waterways carry a lot of the world'strade, majority of the bulky goods, materials and passengers pass through ocean waterways from one country to another at the cheapest cost.
Air transport:air transport is the newest means of transport; it was introduced in 1903 but developed into full means of transporting people and goods in 1930s. The greatest of the air transportation started after the Second World War (WW11). This mode of transportation can be used for both domestic and international flights.
Pipeline transport:this system of transportation involves the use of hollow pipes in the transportation of water, crude oil, (petroleum) and gas. This mode of transportation is safer than using tankers or trailers in the transportation of these liquids.
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Transport
Transport or transportation is the movement of humans, animals and goods from one location to another. In other words the action of transportation is defined as a particular movement of an organism or thing from a point A to the Point B. Modes of transport include air, land (rail and road), water, cable, pipeline and space. The field can be divided into infrastructure, vehicles and operations. Transport is important because it enables trade between people, which is essential for the development of civilizations.
Transport infrastructure consists of the fixed installations, including roads, railways, airways, waterways, canals and pipelines and terminals such as airports, railway stations, bus stations, warehouses, trucking terminals, refueling depots (including fueling docks and fuel stations) and seaports. Terminals may be used both for interchange of passengers and cargo and for maintenance.
Vehicles traveling on these networks may include automobiles, bicycles, buses, trains, trucks, helicopters, watercraft, spacecraft and aircraft.
Operations deal with the way the vehicles are operated, and the procedures set for this purpose, including financing, legalities, and policies. In the transport industry, operations and ownership of infrastructure can be either public or private, depending on the country and mode.
Passenger transport may be public, where operators provide scheduled services, or private. Freight transport has become focused on containerization, although bulk transport is used for large volumes of durable items. Transport plays an important part in economic growth and globalization, but most types cause air pollution and use large amounts of land. While it is heavily subsidized by governments, good planning of transport is essential to make traffic flow and restrain urban sprawl.
Transporation engeneerinig
Transportation engineering or transport engineering is the application of technology and scientific principles to the planning, functional design, operation and management of facilities for any mode of transportation in order to provide for the safe, efficient, rapid, comfortable, convenient, economical, and environmentally compatible movement of people and goods. It is a sub-discipline of civil engineering. The importance of transportation engineering within the civil engineering profession can be judged by the number of divisions in ASCE (American Society of Civil Engineers) that are directly related to transportation. There are six such divisions (Aerospace; Air Transportation; Highway; Pipeline; Waterway, Port, Coastal and Ocean; and Urban Transportation) representing one-third of the total 18 technical divisions within the ASCE.
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The planning aspects of transportation engineering relate to elements of urban planning, and involve technical forecasting decisions and political factors. Technical forecasting of passenger travel usually involves an urban transportation planning model, requiring the estimation of trip generation, trip distribution, mode choice, and route assignment. More sophisticated forecasting can include other aspects of traveler decisions, including auto ownership, trip chaining and the choice of residential or business location. Passenger trips are the focus of transportation engineering because they often represent the peak of demand on any transportation system.
Transportation engineering, as practiced by civil engineers, primarily involves planning, design, construction, maintenance, and operation of transportation facilities. The facilities support air, highway, railroad, pipeline, water, and even space transportation.[1] The design aspects of transportation engineering include the sizing of transportation facilities (how many lanes or how much capacity the facility has), determining the materials and thickness used in pavement designing the geometry (vertical and horizontal alignment) of the roadway (or track).
Building of roads
Road construction techniques were gradually improved by the study of road traffic, stone thickness, road alignment, and slope gradients, developing to use stones that were laid in a regular, compact design, and covered with smaller stones to produce a solid layer.
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Modern roads tend to be constructed using asphalt and/or concrete.
Very broadly, the construction of roads can be described by three processes:
Setting out.
Earthworks.
Paving construction.
Setting out
This is carried out following the dimensions specified in layout drawings.
A commonly used setting out procedure is the profile board method. A series of boards that show the exact level 1 metre above the completed construction level are placed at intervals along the proposed line of the road. A profile board with a fixed height, called the traveller, is used for controlling the excavated levels between these profile boards. By placing the traveller in the sightline between two level boards, it can be seen whether or not the excavation has been carried out to correct levels and adjusted accordingly.
Earthworks
Earthwork is one of the major works involved in road construction. It involves the removal of topsoil, along with any vegetation, before scraping and grading the area to the finished ‘formation level’. This is usually done using a tractor shovel, grader or bulldozer. Below the formation level, the soil is known as the ‘subgrade’. It is essential that the strength of the subgrade is tested prior to earthwork beginning.
Right-of-Way.
The zone which is marked to lay the road is called the road zone or right-of way.
The higher is the technical classification of the road, the wider is the right-of way
for its construction. The road zone includes such parts of a road as a carriageway, road shoulders, inner and outer slopes, and other parts.
The road surface strip within the limits of which motor vehicles run is called
a carriageway. Usually it is reinforced by means of natural or artificial stone
aggregates. These stone aggregates form the pavement.
The strips of the ground which adjoin the carriageway are called the road
shoulders. The shoulders render lateral support to the pavement. In future the
pavement will always be made of solid materials within the limits of the
carriageway.
To lay the carriageway at the required level above the ground surface a
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formation or roadbed is constructed. It is constructed in the form of embankments
or cuttings with side ditches for drainage and the diversion of water.
The formation includes borrow pits – shallow excavations from which the
soil was used for filling the embankments. It also includes spoil banks. Spoil banks
are heaps of excessive soil remaining after the excavation of cuttings.
The carriageway and shoulders are separated from the neighbouring land by
slopes. The cuttings and side ditches have inner and outer slopes. The junction of
the surface of the shoulders and the embankment slope is called the edge of the
roadbed. The distance between the edges is called the width of the roadbed.
Answer the following questions.
1. What is called the road zone or right-of-way?
2. What parts of a road does the road zone include?
3. What is called a carriageway?
4. Is the carriageway usually reinforced by means of natural or artificial stone
aggregates?
5. What is a roadbed constructed for?
Pavement Structural Layers
To ensure all-year-round operation of vehicles traffic on a road, the
carriageway is covered with a pavement. The pavement is laid on the surface of the
roadbed. It can have rigid or semi-rigid structure. The pavement resists traffic
stresses and climatic factors. The stresses induced in the pavement by motor vehicle wheels attenuate with the depth. This enables the pavement to be designed in the form of a multilayer structure. The pavement consists of the following
layers: the surfacing, the pavement base, the sub-base and the subgrade.
1. Surfacing is the upper and most rigid layer of the pavement. It is comparatively thin, but resists well the abrasion and the impacts caused by the wheels, and also the effect of weather conditions. Usually the surfacing is the most expensive part of the pavement. Surfacing usually comprises two coats or courses – a course and a wearing course. Surface course generally contains superior quality materials.
2. Below the surfacing base coat is the pavement base, a strong bearing layer
of stony material or stone with a binding matrix. This layer is designed to
distribute the individual wheel-loads. The pavement base is not subjected to the
direct action of automobile wheels.
3. The sub-base is a layer of earth or stone materials, resistant to moisture,
inserted when necessary between the pavement base and the roadbed. The sub-base
is made of gravel, slag, soil treated with binding agents, sand, etc. Subbase is often
the main load-bearing layer of the pavement. The primary functions of the subbase
are to provide structural support and improve drainage. The quality of subbase
is very important for the useful life of the road.
4. The subgrade is the native material underneath a pavement. It comprises
the thoroughly compacted upper layers of the roadbed upon which the layers of the
pavement are laid. It is also called formation level.
Answer the following questions.
1. For what is the carriageway covered with a pavement?
2. What structure can the pavement be?
3. What enables the pavement to be designed in the form of a multilayer
structure?
4. How many courses does the surfacing comprise?
5. Where is the pavement base laid?
Rigid and Flexible Pavements
Development of a country depends on the connectivity of various places
with adequate road network. Roads are the major channel of transportation for
carrying goods and passengers. They play a significant role in improving the socioeconomic
standards of a region. Roads constitute the most important mode of
communication in areas where railways have not developed much and form the
basic infrastructure for the development and economic growth of the country. The
benefits from the investment in road sector are indirect, long term and not immediately visible. Roads are important assets for any nation. In the past, gravel road surfaces, cobblestone and granite setts were extensively used, but these surfaces have mostly been replaced by asphalt or concrete.
There are various types of pavements depending upon the materials used.
Basically, all hard surfaced pavement types can be categorized into two groups,
flexible and rigid. Flexible pavements are those which are surfaced with asphalt
materials. These types of pavements are called “flexible” since the total pavement
structure “bends” due to traffic loads. A flexible pavement structure is generally
composed of several layers of materials which can accommodate this “flexing”. On
the other hand rigid pavements are composed of a PCC (Portland Cement Concrete) surface course. Such pavements are “stiffer” than flexible pavements
due to the high modulus of elasticity of the PCC material.
State highway agencies generally select pavement type either by policy,
economics or both. Flexible pavements generally require some sort of maintenance
or rehabilitation every 10 to 15 years. Rigid pavements, on the other hand, can
often serve 20 to 40 years with little or no maintenance. Thus, it should come as no
surprise that rigid pavements are often used in urban, high traffic areas. But, when
a flexible pavement requires major rehabilitation, the options are generally less
expensive than for rigid pavements
Answer the following questions.
1. What role do roads play?
2. How can you characterize the benefits from the investment in road sector?
3. What types of road surfaces were used in the past?
4. What do the variety of pavement types depend on?
5. What groups of pavement types are distinguished?
Asphalt
Asphalt (specifically, asphalt concrete) has been widely used since the
1920s. Most asphalt surfaces are laid on a gravel base, which is generally at least
as thick as the asphalt layer, although some asphalt surfaces are laid directly on the native subgrade. Depending on the temperature at which it is applied, asphalt is
categorized as hot mix, warm mix and cold mix. Cold mix asphalt is often used on lower volume rural roads, where hot mix asphalt would cool too much on the long trip from the asphalt plant to the construction site.
An asphalt concrete surface will generally be constructed for high volume
primary highways having an average annual daily traffic load greater than 1200
vehicles per day. Advantages of asphalt roadways include relatively low noise,
relatively low cost compared with other paving methods, and perceived ease of
repair. Disadvantages include less durability than other paving methods, less
tensile strength than concrete, the tendency to become slick and soft in hot weather
and a certain amount of hydrocarbon pollution to soil and groundwater.
Answer the following questions.
1. Where are most asphalt surfaces laid?
2. What types of asphalt are distinguished depending on the temperature?
3. Which type of asphalt is used on rural roads?
4. What highways is asphalt pavement constructed for?
5. When did road builders start to use asphalt?
Concrete
Concrete surfaces (specifically, PCC) are usually used on roads with heavy
traffic of heavy vehicles and created using a concrete mix of Portland cement,
coarse aggregate, sand and water. In virtually all modern mixes there will
also be various admixtures added to increase workability, reduce the required amount of water, mitigate harmful chemical reactions and for other beneficial purposes. In many cases there will also be Portland cement substitutes added, such as fly ash. This can reduce the cost of the concrete and improve its physical
properties. Concrete surfaces are divided into three common types: jointed plain
(JPCP), jointed reinforced (JRCP) and continuously reinforced (CRCP). Each of
the jointing system types is used to control crack development.
Jointed plain concrete pavement is the most common type of rigid pavement. JPCP
controls cracks by dividing the pavement up into individual slabs separated by contraction joints. JPCP does not use any reinforcing steel but uses dowel bars and tie bars. Today the majority of US state agencies build jointed plain pavements.
Jointed reinforced concrete pavements control cracks by dividing the pavement up into individual slabs separated by contraction joints. However, these slabs are much longer than JPCP slabs, so JRCP uses reinforcing steel within each slab to control within-slab cracking. Today very few of agencies use this design, because it is not recommended as both of the other types offer better performance and are easier to repair.
Continuously reinforced concrete pavements use reinforcing steel rather than
contraction joints for crack control. Cracks are held tightly together by the
underlying reinforcing steel. A number of agencies have made decisions to use
continuously reinforced designs in their heavy urban traffic corridors.
Answer the following questions.
1. What materials are concrete surfaces created from?
2. For what purposes are various admixtures added?
3. What are the main types of concrete surfaces?
4. What type of concrete pavement does not use any reinforcing steel?
5. Why is jointed reinforced concrete pavement used only by very few
agencies?
Other pavements
Composite surface combines Portland cement concrete and asphalt. They are
usually used to rehabilitate existing roadways rather than in new construction.
Bituminous surface treatment (BST) is used mainly on low-traffic roads, but
also as a sealing coat to rejuvenate an asphalt concrete pavement. It generally
consists of aggregate spread over a sprayed on asphalt emulsion or cut-back asphalt cement. The aggregate is then embedded into the asphalt by rolling it, typically with a rubber-tired roller. This type of surface is described by a wide variety of regional terms including "chip seal", "oil and stone" etc.
The ease of application of BST is one reason for its popularity, but another is its flexibility, which is important when roadways are laid down over unstable
terrain that thaws and softens in the spring. Gravel is known to have been used
extensively in the construction of roads by soldiers of the Roman Empire. A granular surface can be used with a traffic volume where the average annual daily traffic is 1,200 vehicles per day or less. There is some structural strength as the road surface combines a sub base and base and is topped with a seal aggregate with emulsion. The decision whether to pave a gravel road or not often depends on traffic volume. Obviously, it is not as durable as concrete or asphalt pavements, but relatively cheap. Pavers generally have the form of pre-cast concrete blocks, are often used for aesthetic purposes. Pavers are rarely used in areas with high-speed
vehicle traffic. Brick, cobblestone, sett pavements were once common in urban areas throughout the world, but fell out of fashion in most countries, due to the high cost of labor required to lay and maintain them, and are typically only kept for historical or aesthetic reasons. In some countries, however, they are still common in local streets.
Answer the following questions.
1. What other types of pavement did you learn from the text?
2. For what purposes are composite surfaces used?
3. What materials does BST consist of?
4. Why is BST so popular?
5. When was gravel road extensively used?
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