Major modes of transportation

1. Highways or roadways- the only mode of transportation giving maximum services also the only possible door-to-door service giving mode. Maximum flexibility can be achieved with reference to routes, direction, time and speed of travel.
2. Railways- are advantageous for long distance travel for both passenger and goods. Full advantage of this mode should be taken where railway trucks are available to transport bulk goods along land.
3. Waterways- the slowest mode among the other modes of transportation nevertheless it require less energy to haul unit load through unit distance.
4. Airways- the fastest mode among the other modes of transportation. Additionally it is more comfortable and safe.
In addition to these major modes of transportation there are other modes of transportation like:-
Pipelines to transport fluids like gas, oil, water
Elevators to transport passengers and goods
Conveyers used to transport soil materials
1.6 Route Selection & Preparation of Route
A route should be selected and prepared very carefully as improper selection would result may some of this demerit like increasing in cost of construction, increase in maintenance and transportation etc. However the routes fulfill the following requirement. First it should be straight or short:-the route is desirable if it is straight or short between the two terminal stations. Secondly, the route should be in such away that it is easy to construct and maintain the route with minimum problem. Also the alignment should be easy for the operation of vehicles with easy gradient and curve. Thirdly the rout should be safe enough for contribution and maintenance of road form the view point of natural hill slopes, embankment and cut slopes and foundation of embankment. Also it should be safe for the traffic operation with safe geometric features. Finally to prepare the route, the route alignment could be considered economical only if the total cost including initial cost, maintenance cost and vehicles operation cost is lowest. The route alignment should be such that it would offer maximum utility by serving maximum population and product. The utility of road should be judged from its value per unit length of route.
Requirements of Route Selection
The basic requirements of an ideal alignment between two terminal stations are that it should be:
* Short * Safe, and
* Easy * Economical
Short: it is desirable to have a short (or shortest) alignment between two terminal stations. A straight alignment would be the shortest; through there may be several practical considerations, which would cause deviation from the shortest path.
Easy: the alignment should be such that it is easy to construct and maintain the road with minimum problems. Also the alignment should be easy for the operation of vehicles with easy gradients and curves.
Safe: the alignment should be safe enough for construction and maintenance form the view point of stability of natural hill slopes, embankments an cut slopes and foundations of embankments, also it should be safe for the traffic operation with safe geometric features.
Economical: The road alignment could be considered economical only if the total cost including initial cost, maintenance cost and vehicle operation cost is lowest. All these factors should be given due consideration before working out the economics of each alignment. The alignment should be such that it would offer maximum utility by serving maximum population and products. The utility of a road should be judged from its utility value per unit length of road.
1.7 Factors Controlling Route Alignment
In order to suggest the possible route of a road the topographic and photographic maps of the area should be available with good counter intervals showing the main features like rivers, hills, valleys, churches, mosques, national parks etc. for the alignment to be shortest it should be straight between the terminal stations. This is not always possible due to various practical difficulties such as intermediate obstruction and topography. A shortest route may have very steep gradient and hence not easy for vehicle operation. Similarly there may be construction and maintenance problem along a route, shortest route in order to cater for intermediate place of higher importance or obligatory points.
The various factors, which control the highway alignment, in generally are:
• cost
• traffic
• stability
• environment factors
• obligatory points
• geometric design factors
• drainage
o Cost: the alignment-finalized base on the other factors should also be economical. In working out the economics, the initial cost the cost, of maintenance and vehicle operation should be taken in to account. The initial cost of construction can be decreased if high embankment and cutting are avoided and the alignment is chosen in a manner to balance cutting and filling.
o Obligatory point: there are control points governing the alignment of the high ways. These control points may be divided in to two categories.
I- points through which the alignments is to pass.
II- points through which the alignment should not pass.
I- obligatory point through which the road alignment has to pass may cause the alignment to often deviate from the shortest or easiest path. The various examples of this category may be bridge site, intermediate town, a mountain pass or a quarry. When it is necessary to cross – hill range, mountains of high rides the various alternatives are to cut tunnels across or to go round the hills or to deviate until a suitable hill pass is available. The suitability of these alternatives depends on many other factors like the topography and site condition and cost consideration.
The road bridge across a river can be located only at the place where the river has straight & permanent pass and where the bridge abutment and pier can be properly founded. The road approaches to this bridge should not be curved near the bridge and as far as possible the skew crossing should be avoided. Thus in order to locate a bridge across a river the alignment may have to be changed. Fig.1-b show that the straight alignment between stations A&B which passes through the river bends, is to be deviated along the path shown in order to cross the river at a proper bridge location at the straight portion of the river on the up stream side of the band.
While aligning a road between two stations, it may often be desirable to connect some of the important intermediate towns, villages or other places.
II- Obligatory points through which the road should not pass also may make it necessary to deviate from the proposed shortest alignment. The obligatory points which should avoided while aligning a road, include religious place, very costly structures, un suitable lands etc. the law from being acquired for any purpose has protected religious place like template, mosque, church, grave or tomb. Acquiring costly structures would mean heavy compensation resulting in increase cost. Marshy, peaty and waterlogged areas are generally unsuitable for road construction and should be avoided as far as possible. However, if there is no alternative the alignment has to be taken across such an area, the construction and maintenance cost are likely to be very high due to special construction techniques and drainage measures to adopted.
A lake, pond or a valley which falls on the path of a straight alignment will also necessitate the alignment to deviate from the straight path and go round along the grade line.
Traffic: the alignment should suit traffic requirements. Origin and destination study should be carried out in the area and the desirable be drawn showing the trend of traffic flow. The new road to be aligned should keep in view the desire lines, traffic flow patterns and future trends.
Geometric design: geometric design factors such as gradient, radius of curve and sight distance also will govern the final alignment of the high way. If straight alignment is aimed at often it may be necessarily provide very steep gradient. As far as possible while aligning a new road, the gradient should be flat and less than the ruling or design gradient. Thus it may be necessary to change the alignment in view of the design speed, maximum allowable supper elevation and coefficient of lateral friction. It may be necessary to make adjustment in horizontal alignment of road keeping in view the minimum radius of curve and transition curves
The absolute minimum sight distance, which should invariably be available in very section of the road, is the safe stopping sight distance for the fast moving vehicles. Also there should be enough distance visible ahead for safe overtaking operations of vehicles moving at design speed on the road. Hence, the alignment should be finalized in such away that the obstruction to visible does not cause restriction to the sight distance requirements.

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