Highway development and planning: importance, classification of roads, road patterns, planning surveys; highway alignment and surveys PDF

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I.

Highway Development and Planning

Quoted from Highway Planning PDF

Highway engineering is an engineering discipline branching from Civil Engineering that involves the planning, design, construction, operation, and maintenance of roads, bridges, and tunnels to ensure safe and effective transportation of people and goods. Highway planning involves the estimation of current and future traffic volumes on a road network. The Highway planning is also a basic need for the Highway development. Highway engineers strive to predict and analyze all possible civil impacts of highway systems. Some considerations are the adverse effects on the environment, such as noise pollution, air pollution, water pollution, and other ecological impacts According to Mugdha, planning is a prerequisite for any engineering activity or project; this is particularly true for the development of a highway network or system in a country. According to Sirisha (2014), transportation involves movement of persons and goods from one place (origin) to another (destination). The principles of science and mathematics such that various properties of matter and sources of energy in nature (diesel, petrol, electricity produced from coal, water etc.) are utilized to move persons and goods in a manner useful to mankind and at minimum cost. Moreover, we shall study about salient characteristics of various transportation systems with respect to land (highways and railways, water ways and also airways).

A. Importance The objectives of highway planning are (a) Planning a highway network for safe, efficient and fast movement of people and goods, (b) Keeping the overall cost of construction and maintenance of the roads in the network to a minimum, (c) Planning for future development and anticipated traffic needs for a specific design period, (d) Phasing road development programs from considerations of utility and importance as also of financial resource, and (e) Evolving a financing system compatible with the cost and benefits. In order to fulfill these objectives, first, the proposed road links should be a part of the planned road network for the state/nation. The suggested road links must consider and dependent on the current state of the area’s road plan. Second, the importance of the road shall be based on the traffic demand, and hence its type should fall under the standard classification. Third, the maintenance needs of the roads should receive prompt attention by setting aside funds for this purpose. And last principle that highway Engineers must have to borne in mind is that the statutory provisions for traffic regulation should be in place. The importance of highway planning are briefly given below:

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To plan a road network for efficient and safe traffic operation, but a minimum coast. Here the costs of construction, maintenance and renewal of pavement layers and the vehicle operation costs are to be given due construction. To arrive at the road system and the lengths of different categories of road which could provide maximum utility and could be constructed within the available resource during the plan period under construction. To fix up date wise priorities for development of each road link based on utility as the main criterion for phasing the road development program. To plan for future requirements and improvement of roads in view of anticipated developments. To work out financing system

B. Classification of Roads Quoted from engineeringnotes.com

The classification of roads depends on the criterion considered. An All-Weather Road is a road that is trafficable in all weather conditions. Typically this means a road that is constructed in such a way that excessive rain does not cause it to be flooded or sodden to such an extent that vehicles travelling over it are likely become bogged. Fair weather roads, if traffic is interrupted during monsoon at course ways where water overflows for a few hours. Based on the type of carriage-way or the road pavement, it may be a paved road with at least a water-bound macadam layer; or it may be an unpaved road. Earth roads and gravel roads fall in this category. Superior paved roads have bituminous surface or concrete surface for the carriage-way. A bituminous road is also known as a black-top road. Traffic volume, load transported per day, and the location and function are important criteria for classification of roads. The classification of roads depends on the criterion considered. They may be all-weather roads if they can be used during all seasons of a year; fair-weather roads, if traffic is interrupted during monsoon at course ways where water overflows for a few hours. Based on the type of carriage-way or the road pavement, it may be a paved road with at least a water-bound macadam layer; or it may be an unpaved road. Earth roads and gravel roads fall in this category. Superior paved roads have bituminous surface or concrete surface for the carriage-way. A bituminous road is also known as a black-top road.

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Traffic volume, load transported per day, and the location and function are important criteria for classification of roads. These criteria have been taken into account in the classification recommended by the Nagpur Plan—NH, SH, MDR, ODR and VR, as also in the one modified by the Lucknow Plan —with categories of Primary, Secondary and Tertiary roads. Urban roads are classified based on their function and location: 1.

Expressways— for movement of heavy volume of traffic.

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(ii) Arterial streets—for connecting the central area to expressways. (iii) Sub-arterial streets—similar to arterial roads but with less spacing. (iv) Collector streets—for collection and distribution of traffic through local streets in residential areas. (v) Local streets—to access private property like residences, shops and industries. Traffic originates here or ends here.

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In this context, certain definitions are relevant: (i) Road – A convenient way over which vehicles may lawfully pass for going 1. from one place to another. (ii) Service road – Used for servicing and as a means of access to adjacent 2. property; constructed parallel to the main road adjacent to roadside buildings. (iii) Street – A road within a town or a residential locality with buildings on one or 3. both sides. (iv) Country road – Road connecting one place to another on the country-side. 4. 5. (v) Urban road – A road within a town or a city. (vi) Bypass road – A road constructed skirting a village or a small town, taking 6. off through a highway and joining it after bypassing the inhabited area; this helps through traffic to move fast without having to enter the village or town. 7. (vii) Highway – Any public road or a street may be called a highway. (viii) Arterial road – Road passing within a city and linking the state or national 8. highway, with limited access. 9. (ix) Freeway – An arterial highway with controlled access crossing other roads at different levels. (x) Boulevard – Very wide road with avenue on its either side; generally used 10. for ceremonial processions or considered as prestigious roads in a city.

C. Road Patterns and Planning Surveys Quoted from Highway Planning PDF

Urban Road Patterns:

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Although road patterns in a country are historically inherited, later additions can be planned bearing in mind the requirements of the day. Road patterns are of great use in urban highway planning. The choice of a road pattern depends upon the extent of land use or the distribution of residential, industrial and business areas in a city, the nature of the terrain, and the planner’s preferences. The main patterns in use in urban areas are: 1. Grid Iron Pattern: This is also known as rectangular or block pattern and is perhaps the simplest (Fig. 1.5). The Romans preferred it, as have the Americans who adopted it in many of their cities. This is easy to set out in straight lines and rectangular co-ordinates, and is suitable for flat terrain.

The disadvantages of this pattern are monotonously long streets and the inconvenience in traffic operation. There are also certain advantages such as bypassing any road with traffic congestion and the convenience of imposing one-way traffic, if necessary, making alternate streets with one- way traffic in opposite directions. Chandigarh city is an excellent example of this pattern. Recently developed localities in most major cities such as Bangalore City have been built on this pattern. 2. Radial Pattern: In this pattern, roads emanate from a central focal area, which may be a business centre or an important public building. In order to ease the congestion in the focal area, ring roads are provided; there can be several such roads—inner, intermediate and outer—depending on the requirements of the traffic. The shape of a ring road may be round, square, or elongated. Based on this, the pattern may be star and grid, or star and circular. The star and grid pattern, or the radial and block pattern has been the basis of the Nagpur Road Plan, and it has been adopted in a number of Indian cities (Fig. 1.6).

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The star and circular pattern, also known as the radial and circular pattern, has been adopted in certain cases, although in a limited way. A classic example is the Connaught Place area of New Delhi. (Fig. 1.7)

3. Hexagonal Pattern: The basic figure of the road network in this case is a hexagon; each hexagon has at least one side common with an adjacent pattern, as shown in Fig. 1.8.

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The hexagonal pattern can be modified by dividing the hexagon into six triangle units by link roads; this facilitates travel from one place to any other place in the area in the minimum possible time, compared to any other pattern. This, in fact, is known as a ‘minimum travel pattern’ and was used in certain cities to great advantage. Quoted from EduRev

Planning Surveys For assessing the road length requirements, following studies are made: 1. Economic Studies - Details of the existing facilities, their utility, distribution of the existing population in the area, population growth trends, existing products in the agricultural and industrial sectors, future trends of development in these sectors, existing communication and education facilities, and the per capita income are to be collected. 2. Financial Studies – source of income; Various financial aspects such as the sources of funding, estimated revenue from taxes on vehicles, toll tax, and indirect benefits of raising the living standards of the people due to the proposed road network are considered. 3. Traffic or road use studies - Details of the existing road facilities, traffic volume in vehicles per day, traffic flow patterns, classes of traffic such as passenger cars, busses and trucks, loads carried, average speeds, anticipated future trends of traffic growth, and other traffic-related studies are to be conducted. 4. Engineering studies - These include study of the topography, soil, road life and special problems, if any, relating to construction, drainage and maintenance. A systematic study of all these data will help the planner in the preparation of a Master Plan to serve the needs of the area for a specified design period of say, 20 to 25 years.

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Saturation system for calculating optimum road length In this the option road length us calculated for area, based on the concept of obtaining maximum utility per unit length of road. Hence, this system is called saturation system of maximum utility system. Factors for obtaining the utility per length of road are: 1. Population served by the road 2. Productivity served bt the road network a. Agricultural product b. Industrial products After deciding the optimum road length for plan period., the final step is the phasing of the road development plan by fixing up the priorities fot eh construction of different road links. Quoted from fao.org

Route Planning Planning with respect to road construction takes into account present and future uses of the transportation system to assure maximum service with a minimum of financial and environmental cost. The main objective of this initial phase of road development is to establish specific goals and prescriptions for road network development along with the more general location needs. These goals must result from a coordinated effort between the road engineer and the land manager, forester, geologist, soil scientist, hydrologist, biologist and others who would have knowledge or recommendations regarding alternatives or solutions to specific problems. The pattern of the road network will govern the total area disturbed by road construction. The road pattern which will give the least density of roads per unit area while maintaining minimum hauling distance is the ideal to be sought. Keeping the density of roads to an economical minimum has initial cost advantages and future advantages in road maintenance costs and the acreage of land taken out of production. Sediment control design criteria may be the same as, or parallel to, other design criteria which will result in an efficient, economical road system. Examples of overlap or parallel criteria are: 1. Relating road location and design to total forest resource, including short and long term harvest patterns, reforestation, fire prevention, fish and wildlife propagation, rural homestead development, and rangeland management.

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2. Relating road location and design to current and future timber harvesting methods. 3. Preparing road plans and specifications to the level of detail appropriate and necessary to convey to the road builder, whether timber purchaser or independent contractor, the scope of the project, and thus allow for proper preparation of construction plans and procedures, time schedules, and cost estimates. 4. Writing instructions and completing companion design decisions so as to minimize the opportunity for "changed conditions" during construction with consequent costs in money and time. 5. Analyzing specific road elements for "up-front" cost versus annual maintenance cost (for instance, culvert and embankment repair versus bridge installation, ditch pavement or lining versus ditches in natural soil, paved or lined culverts versus unlined culverts, sediment trapping devices ("trash racks", catch basins, or sumps) versus culvert cleaning costs, retaining walls or endhauling sidecast versus placing and maintaining large embankments and fill slopes, roadway ballast or surfacing versus maintenance of dirt surfaces, and balanced earthwork quantities versus waste and borrow). The route planning phase is the time to evaluate environmental and economic tradeoffs and should set the stage for the remainder of the road development process. Although inclusion of design criteria for sediment control may increase initial capital outlay, it does not necessarily increase total annual cost over the life of the road which might come from reductions in annual maintenance, reconstruction, and repair costs (see Section 2.2). If an objective analysis by qualified individuals indicates serious erosional problems, then reduction of erosional impacts should be a primary concern. In some areas, this may dictate the location of control points or may in fact eliminate certain areas from consideration for road construction as a result of unfavorable social or environmental costs associated with developing the area for economic purposes.

D. Highway Alignment and Surveys Quoted from engineeringnotes.com

Highway Alignment: The laying out of the centre line of a proposed highway on the ground is called its ‘alignment’. A new road should be aligned carefully since any change in alignment may not be possible or may be expensive at a later stage, owing to increased land acquisition costs and roadside structures constructed after the road has taken shape. Requirements of an Ideal Alignment:

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1. Directness: The aligned route between end points should be as direct as possible and result in the minimum possible length under the circumstances. 2. Ease of Construction, Maintenance and Operation: The alignment should be such that it is easy to construct, maintain and operate the highway. The curves and gradients should be easy. 3. Safety: Safety for the road-users should be the primary consideration; the stability of natural slopes and man-made slopes for embankments and cuttings should be ensured to prevent possible accidents. 4. Economy: The overall cost of construction and maintenance of the road, as also the operation cost of the vehicles should be as low as possible. 5. Special Considerations: Depending upon the purpose of the highway and the characteristics of the terrain, special considerations may be needed as in the case of hill roads or ghat roads.

Horizontal and Vertical Alignment Quoted from engineeringnotes.com

This is the alignment of the roadway in the horizontal plane; although it is ideal to have a straight route between end points, it is practically impossible owing to several constraints. A change in direction necessitates the use of horizontal curves for smooth flow of traffic. Quoted from fao.org

For low volume roads with design speeds of 24 kph (15 mph) or less, a horizontal alignment that approximates the geometric requirements of circular curves and tangents may be used. Alignment should be checked so that other design elements, such as curve widening and stopping sight distance can be considered. A minimum centerline radius of curvature for roads should be 15 meters (50 ft) except for some recreation and administrative roads. Superelevation should not be used for design speeds less than 32 kph (20 mph). If snow and ice are factors, the superelevation rate should not exceed 6 percent and should be further reduced on grades to accommodate slow truck traffic. Transition segments into and out of superelevated sections should be provided to avoid abrupt changes in the roadway template. Quoted from engineeringnotes.com

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Although it is ideal to have a roadway at the same elevation throughout, this is almost impractical and gradients or slopes along the length become mandatory. A change in gradient calls for curves in the vertical plane; vertical curves should be designed and constructed for smooth flow of traffic based on several criteria. The alignment may be smoothened as shown in Fig. 2.1:

Quoted from fao.org

Vertical alignment, or grade; is of critical concern because of its potential for environmental damage and becomes increasingly important for grades exceeding 10 percent. Erosion potential increases as a function of the square of the slope and the cube of water velocity. The Most desirable combination of grade and other design elements should be determined early in the road location phase with additional caution exercised when grades exceed 8 percent. Vertical alignment normally governs the speed of light vehicles for grades exceeding 15 percent favorable and 11 percent adverse and of loaded trucks for grades exceeding 8 percent favorable and 3 percent adverse. The ability of a vehicle to traverse a particular grade is dependent on vehicle weight and horsepower and on the traction coefficient of the driving surface. Travel time and cost are affected by horizontal alignment, such as curve radius and road width. Figure 9 shows the relationship between average truck speed and curve radius for several road widths. For example, there is a 15 percent difference in average truck speed on a 30.5 m (100 ft) radius curve for a 3.7 m wide road when compared to a 4.3 m wide road. Horizontal alignment has been classified on the basis of curve radius and number of curves. The U. S. Forest Service, for example, uses the following classification system:

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[Average radius (m)] / [# of curves / km] Poor

Fair

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< 4

Good

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