Preparation of Plans:

• Plan 1: A general map of the area that depicts nearly all of the existing features, including terrain, current road networks, drainage systems, rivers, populated villages, agricultural land, etc.
• Plan 2: The distribution of demographic groups based on the classifications established in the relevant plan.
• Plan 3: Displays the locations of several locations together with their corresponding levels of productivity.
• Plan 4:  Displays the current road network along with studies of traffic patterns. suggested fresh and different routes.

Interpretation of Planning Surveys:

• To select the road network among alternative options that offers the most utility.
• To organise construction projects according to priority and phase the development plan.
• Examining traffic flow patterns to gauge actual road usage.
• The investigations are used to develop structural and geometric aspects.
• The economic activity of the regions can be used to compare them. vi) On a statistical basis, the information gathered from fact-finding surveys can be examined for potential patterns in the future growth of a region.

Master Plan:

Road development plans for a city, area, street, or a whole country are referred to as master plans. It is a perfect blueprint that depicts the area’s entire growth at a later time. It acts as the blueprint for the plan to build a network of new roads and to make some improvements to some of the current ones. It aids in regulating the development of the area’s industrial, commercial, agricultural, and environment in a methodical manner. It presents a realistic image of a fully built place in a planned and methodical manner.

Stages in the Preparation of Master Plan:

• Data collection: This includes information on current land use, agricultural and industrial expansion, population growth, traffic patterns, geography, and emerging trends.
• Creation of a draught plan and solicitation of public and expert feedback.
• The draught plan was revised in light of the debates and suggestions made by professionals and the general public.
• Comparing different alternative road system proposals and determining the order in which the master plan will be implemented. Based on population, area, and agricultural and industrial output, many road plans in India set target road lengths. When creating a master plan for a town or locality, it can be used as a guide to determine the overall length of the road system in each alternative proposal.

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• Determination of the area’s needed road length
• Creation of a master plan that demonstrates how the strategy will be phased in over either five or annual plans

The planning surveys consists of the following studies

• Economical Studies
• Financial studies
• Traffic or road use studies
• Engineering studies.

Economic Studies:

Estimating the needs, costs, and economic justification for the proposed highway improvement programme is made possible by the information that will be gathered during economic studies. It is crucial to initially gather all information regarding the current facilities, any shortcomings, potential trends, and the expected cost of improvements.

The following are some of the various details that need to be gathered for economic studies.

• Distribution of the population.
• population growth trend
• Agricultural and industrial items, as well as their region-based classification.
• Future trends and industrial growth
• Per capita income
•  Existing educational, medical, and recreational facilities.

Financial studies

The many financial issues, such as income sources and potential methods of raising funding for the project, must be studied through financial studies, which are crucial.

The following information has to be gathered:

• Revenue sources and projections from road transportation and taxes.
• Living conditions.
• Locally accessible resources, toll fees, vehicle registration fees, and fines.
• Proposed financial aspects trends.

Traffic or road use studies

Before taking any action, every aspect of the current traffic, including its volume and flow pattern, must be known.

There is potential for improvement.

The following information has to be gathered:

• The number of vehicles on the road each day and peak hourly traffic.
• Research on origin and destination.
• The movement of traffic.
• Infrastructure for mass transit.
• Accidents, their causes, and a cost analysis.
• Increased traffic volume and future trends.
• An increase in passenger travel and a trend in mode selection

Engineering Studies

Before taking any action, every aspect of the current traffic, including its volume and flow pattern, must be known.

There is potential for improvement.

The following information has to be gathered:

• The number of vehicles on the road each day and peak hourly traffic.
• Research on origin and destination.
• The movement of traffic.
• Infrastructure for mass transit.
• Accidents, their causes, and a cost analysis.
• Increased traffic volume and future trends.
• An increase in passenger travel and a trend in mode selection

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Back Tangent: The tangent line (AT1) before the beginning of the curve is called the Back tangent or the rear tangent.

Froward Tangent: The tangent line (T2B) after the end of the curve is called the Forward tangent. The distinction of the back tangent from the forward tangent depends on the direction of the route surveying.

Point of Intersection (P.I.): The point at which the extension of the back tangent and the forward tangent meet is known as the Vertex (V) or point of intersection (P.I.).

Point of Curvature (P.C.): The point on the back tangent where the curve begins is known as the Point of Curvature (P.C.). At this point, the alignment of the route changes from a straight line to a curve. This is represented by T1

Point of tangency (P.T.): The point on the forward tangent where the curve ends is known as the Point of tangency (P.T.). At this point, the alignment of the route changes from a curve to a straight line.

Intersection angle: The exterior angle at the vertex or point of intersection is known as the Intersection angle ( ). It is also known as the Deflection angle as it represents the deflection angle between the back tangent and the forward tangent. Thus, the angle between the line AV’ produced and the line VB represents the intersection angle or deflection angle.

Deflection angle to any point: The deflection angle to any point on the curve is the angle at P.C between the back tangent and chord from P.C to the point on the curve

Tangent distance (T): The distance between the point of curvature (T1) to the point of intersection (V) along the extension of the back tangent is known as Tangent distance (T). It is also equal to the distance between the points of tangency (T2) to the point of intersection along with the extension of forward tangent.

External distance (E): The distance between the point of intersection (V) and the middle point of the curve is called as External distance (E).

Length of curve (l): The length of the alignment along the curve between the point of curvature (T1) and the point of tangency (T2) is known as the Length of curve (l).

Long chord (L): The longest possible chord of the circular curve is known as Long chord. It is the line joining the point of curvature (T1) and the point of tangency (T2).

Mid ordinate (M): The distance between the middle point of the curve and the middle point of the long chord is Mid-ordinate (M).

Normal Chord (C): A chord between two successive regular stations on a curve. Normally, the length of normal chord is 1 chain.

Sub chord(c): The chord shorter than normal chord is called sub chord. (Fig(1.3.2))

Right hand curve: If the curve deflects to the right of the direction of the progress of survey.

Left hand curve: If the curve deflects to the left of the direction of the progress of survey.

Central angle: The central angle is the angle formed by two radii drawn from the center of the circle (0) the PC and PT. The central angle is equal to the Intersecting angle.

Designation of a Curve:

A curve is designated either in terms of its degree of curvature (D) or by its radius (R).

The degree of a curve (D) is defined as the angle subtended at the centre of the curve by a chord or an arc of specified length. The degree of curvature has several slightly different definitions.

Chord Definition:

The degree of a curve is defined as the angle subtended at the centre of the curve by a chord of 100 ft length.

Metric Degree of Curve

In the metric system two degrees of curve are in use:

1. Angle at center subtended by an arc of 20m
2. Angle at center subtended by an arc of 10m

If the definition is based on 20m

R = 1146/D

If the definition is based on 10m

R = 573/D

Setting out of simple curve:

The various methods used for setting curves may be broadly classified as:

1. Linear methods

In this method, only a chain or tape is used. Linear methods are used when,

• A high degree of accuracy is not required
• The curve is short

The following are some of the linear methods used for setting out simple circular curves:

• Offsets from long chord
• Successive bisection of chord
• Offsets from the tangents–perpendicular or radial
• Offsets from the chords produced.

2. Angular methods

In this method an instrument such as theodolite is used with or without a chain. The following are the angular methods which can be used for setting circular curves:

• Rankine method of tangential (deflection) angles.
• Two-theodolite method
• Tacheometric method

Before setting out of curve it is essential to locate the tangents, point of intersection, point of curvature and point of tangency. Before setting out the curve, the surveyor is always supplied with a working plan upon which the general alignment of tangent is known in relation to the traverse, controlling the survey of the area. Knowing offsets to certain points on both the tangents, the tangents can he staked on the ground the tape measurements. The tangents can be set out by theodolite and the total deflection angle can then be measured by setting theodolite on the P.I. After having located the P.I and measured the tangent length (T) can be calculated from equation

(T) = R tan (D/2)

The point T1 can be located by measuring back a distance VT1 = T on the rear tangent.

Similarly, the point T2, can be located by measuring a distance V T2 = T on the forward tangent.Knowing the chainage of P.I. the chainage of point T1 can be known by subtracting the tangent length from it. The length of the curve is then added to the chainage of T1 to get the chainage of T2.For the ease in calculations and setting out, it is essential that the pegs on the curve are at regular interval from the beginning to the end. Such interval is known as peg interval and the chord joining two such adjacent pegs is known as the full chord or normal chord. The length of the normal chord is generally taken equal to 100 ft in English units or 20 metres in metric units, so that angle subtended by the normal chord at the centre is equal to the degree of the curve. The stations having the chainages in the multiples of chain lengths are known as full stations. The distance between the point T1 and the first peg will be less than the length of the normal chord so that the first chord joining the point of curve T1 to the first peg will be a sub-chord. Similarly, the last chord, joining the last peg on the curve and the tangent point T2 will be a subchord. All other intermediate chords will be normal chords or units chords.

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Curves are commonly utilised on highways and railways where the direction of travel must be changed. When a road or railway changes direction from right to left (or vice versa) or changes alignment from up to down, curves are supplied (vice versa). Curves are a really important aspect of pavement design They are given a maximum speed limit that should be followed carefully adhered to. Following the speed limit becomes critical because exceeding it may result in injury increase the likelihood of the vehicle losing control when negotiating a turn, and consequently increase the likelihood of deadly collisions. A curve is defined as an arc between crossing straights (tangent) with a finite radius. Negotiate a shift in direction gradually.

Classification of Curves:

The centre line of a road consists of a series of straight lines interconnected by curves that are used to change the alignment, direction, or slope of the road. Those curves that change the alignment or direction are known as horizontal curves, and those that change the slope are vertical curves. It can be also defined as the curves provided on the horizontal plane are horizontal curves and curves provided on the vertical plane are vertical curves.

Types of Horizontal Curve:

There are four types of horizontal curves. They are described as follows:

Simple Curves:

A simple arc of a circle is provided to impose a curve between the two straight lines.

Compound Curve:

Combination of two simple curves combined together to curve in the same direction and join at common tangent points.

Reverse curve:

A reverse curve consists of two simple curves of the same or different radius joined together but curving in opposite directions.

Spiral curve:

The spiral is a curve that has a varying radius. It is used on railroads and most modem highways. Its purpose is to provide a transition from the tangent to a simple curve or between simple curves in a compound curve.

Vertical curves:

In addition to horizontal curves that go to the right or left, roads also have vertical curves that go up or down. Vertical curves at a crest or the top of a hill are called summit curves, or over verticals. Vertical curves at the bottom of a hill or dip are called sag curves, or under verticals

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