The importance of motor roads for the national economy is closely related to the intensity of traffic on them, i.e., the higher the traffic intensity, the better should be the standard of design. Where traffic intensity is high the expenditure necessary for the construction of the road to follow the most direct route and with shallow gradients will soon be compensated by the economy in traffic operation. On the other hand, if in spite of a high traffic intensity the road is built with steep gradients and a narrow carriageway, though its capital cost may be much lower it will not permit the most effective performance of vehicles to be realized, in particular the maintenance of high vehicle speeds. In the long run, the cost of motor transport operation would become excessive.
The question of choice of the type of road, however, does not depend exclusively on the cost of construction. A number of other factors must be taken into consideration, particularly the part to be played by the specific highway in the transport system of the national economy.
There is a number of roads which are built according to high technical standards in spite of their comparatively low traffic intensity.
When designing roads to be constructed in new, sparsely populated regions, the expected traffic intensity cannot be the only criterion. In spite of the expected low traffic intensity for a number of years to come, such roads will constitute the main artery for populating these regions, Therefore, such roads can be built with a view to district, development, according to technical standards corresponding to a traffic intensity exceeding the present rate.
The motor roads are divided into five technical classes. The class is determined according to the importance of the road for the national economy. At the same time potential traffic intensities are considered, as well as the construction difficulties arising from the topographic features of thecountry in which the road is to be located.
The elements of the plan, profile and cross-section are designed with a view to the traffic intensities to be expected in 20 years, and the road pavement - in 5 to 10 years, depending on its construction and the possibility to strengthen it gradually.
Class I comprises roads having special economic, administrative or cultural importance for the national economy and having a high initial or potential traffic intensity; class II comprises similar roads with an appreciable potential traffic intensity; class III covers motor roads with a moderate traffic intensify but having a very.great importance for the national economy of the republics class IV includes roads having.local economic, administrative or cultural importance and a low traffic intensity; and 1ass V covers motor roads with small initial and potential traffic intensity.
All road elements of each technical class are designed to ensure the safe running of vehicles under normal conditions of cohesion between vehicle wheels and the carriageway surface.
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Test 2. Freeway.
A freeway is a type of highway designed for safer high-speed operation of motor vehicles through the elimination of at-grade intersections. Such highways are usually divided with at least two lanes in each direction. Because traffic never crosses at-grade, there are generally no traffic lights or stop signs.
Freeways, by definition, have no cross traffic in the form of other roads or railroads. Elimination of cross traffic is typically achieved with grade separation in the form of underpasses and overpasses. In addition to sidewalks attached to roads that cross a freeway, specialized pedestrian bridges or tunnels may also be provided. These structures enable pedestrians and cyclists to cross the freeway without a long bypass to the nearest motor vehicle crossing. In many areas, travelers using low-powered modes of transportation (such as pedestrians, bicyclists and moped drivers) are banned from freeways. These users are allowed on freeways in some jurisdictions, usually where freeways too often replaced existing roads.
The word "freeway" first appeared in the mid-1930s in proposals for the improvement of the New York City parkway network. It is currently in regular use in the United States, as well as parts of Canada and Australia.
Speed limits are generally higher than on similar non-freeways, and are sometimes nonexistent. Because the high speeds reduce decision time, freeways are usually equipped with a larger number of guide signs than other roads, and the signs themselves are physically larger. In major cities, guide signs are often mounted on overpasses or overhead gantries so that drivers can see where each lane goes.
In most areas, there are public rest areas or service areas on freeways, as well as emergency phones on the shoulder at regular intervals.
Freeways reduced travel times and accident rates, though the higher speeds have increased the severity and death rates of the collisions.
Freeways have been heavily criticized by environmentalists, urbanists, and preservationists for the noise, pollution, and economic shifts they bring. Additionally, they have also been criticized by the driving public for the inefficiency with which they handle peak hour traffic.
at-grade intersection -
grade separation -
underpass ;
overpass - ,
gantry -
Section III.Oral Presentation:1. Maintenance
Construction
Maintenance
The life of a road structure depends on the quality of its maintenance and minor renovation. Maintenance keeps the roadway safe, provides good driving conditions, and prolongs the life of the pavement, thus protecting the road investment. Maintenance consists of activities concerned with the condition of the pavement, shoulders, drainage, traffic facilities, and right-of-way. It includes the prompt sealing of cracks and filling of potholes to prevent water entering through the surface, the removal of trash thrown on the wayside by the traveling public, and the care of pavement markings, signs, and signals. In rigorous winter climates, substantial effort is required to remove snow and ice from the pavement, to scatter salt for snow and ice removal, and to spread sand for better traction.
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In many countries an increasing share of road budgets is being allocated to rehabilitation and maintenance of existing roads, rather than new road construction.
Routine maintenance refers to activities such as grading, grass cutting, drain clearing, pothole patching, and shoulder repairs, which are performed at least yearly if not more frequently. Periodic maintenance activities are typically scheduled over periods of several years and include resurfacing and bridge repairs. Rehabilitation involves more substantial intervention to strengthen a road, repair structural defects, and restore the road to its initial condition, often after it has deteriorated to an "unmaintainable" standard. Rehabilitation sometimes also includes changes or improvements to previous characteristics, for instance, by widening, making small alignment changes, or providing footpaths.
Other maintenance activities include seasonal maintenance, such as snow clearing and flood repairs, emergency maintenance to reinstate roads after major failures, and the regular upkeep of safety features and road signs.
Construction.
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.
Firstly the longitudinal and vertical alignment of the road is set out by a surveyor. The alignment of the road will be marked with control pegs. The pegs will have level markings as a control mechanism to ensure the road is constructed to the appropriate design levels.
Construction of the road commences with the stripping of the topsoil, within the road reserve. The topsoil is usually stockpiled nearby for rehabilitation of newly constructed embankments along the road. The in-situ ground will be removed, using a heavy motorised grader to a level specified by the civil engineer. This is considered as the road-bed level. It will be compacted using a heavy vibratory road roller. Once the roadbed has been compacted to the required density (as will be specified by the engineer), the pavement layers can now be imported.
Section IV. Vocabulary:
Accomplish
