Horizontal Alignment

In plan view, the highway’s direction is referred to as its horizontal alignment. The topography of the terrain, environmental restrictions, and the desired speed of the roadway must all be taken into account while planning the horizontal alignment of a highway. The main goal of horizontal alignment is to maintain driver comfort and safety while facilitating effective traffic flow.

The terms tangent, simple curve, complex curve, reverse curve, and transition curve are all examples of horizontal alignments. A simple curve is a length of road that bends at a constant radius, while a tangent alignment is a section of straight pavement. Reverse curves are sections that curve in the opposite way from compound curves, which are sections with two or more curves of different radii. A segment that progressively transforms from a straight section to a curve or vice versa is known as a transition curve.

Vertical Alignment

The term “vertical alignment” describes the highway’s vertical direction. The vertical alignment is intended to take into account a number of variables, including drainage needs, safety concerns, and the terrain of the ground. The main goal of vertical alignment is to give drivers a comfortable, safe, and smooth ride.

Grades, or the slope of the road, and vertical curves, or sections of the road that change from a grade to a flat section, are both considered to be in the vertical alignment. The topography of the ground and the desired speed of the roadway must be taken into account while designing grades, and safety must always come first. Vertical curves must be built such that vehicles may maintain a safe speed and that the transition between different slopes is smooth.

Environment-Related Issues

Civil engineers must take the environment into account when building highway alignment. The building and maintenance of highways can have an impact on a variety of environmental aspects, including wildlife habitats, water supplies, and air quality.

While still ensuring that the community’s transportation needs are met, civil engineers must try to reduce the road’s negative environmental effects. In order to do this, the roadway may need to be designed to avoid vulnerable ecosystems, green infrastructure like bioswales may need to be used to manage stormwater runoff, or alternate modes of transportation like bike lanes or public transportation may be used.

The placement of highways is a crucial component of civil engineering that necessitates careful consideration of a number of aspects, including safety, viability from an economic standpoint, and environmental impact. The alignment of the highway must be designed to fulfil community transportation needs while also maintaining driver comfort and safety and reducing the road’s negative environmental effects. Civil engineers must modify their designs to accommodate society’s changing transportation requirements while still keeping an emphasis on safety and sustainability.

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There are three steps in the process of making road tar:

• Carbonising coal to create crude tar;
• Refining or distilling crude tar; and
• Making the desired road tar by combining distillation residue and distillate oil fraction.

Based on their viscosity and other characteristics, roadways tar comes in five grades: RT-1, RT-2, RT-3, RT-4, and RT-5.

• The paint RT-1, which has a very low viscosity, is used for surface painting in extremely cold climates.
• Under typical Indian weather, RT-2 is advised for standard surface painting.
• For surface painting, renewal coatings, and chip premixing for top course and light carpets, use RT-3.
• Tar macadam is typically premixed in base course using RT-4.
• Among the road tars, RT-5, which has the maximum viscosity, is used for grouting.

The various tests carried out on road tars are:

1. Specific gravity test
2. Viscosity test on standard tar viscometer iii.
3.  Equiviscous temperature (EVT)
4. Softening point
5. Softening point of residue
6. Float test
7. Water content
8. Phenols, percent by volume
9. Naphthalene, percent by weight
10. Matter insoluble in toluene, percent by weight
11. Distillation fraction on distillation up to 2000C, 2000C-2700C and 2700C-3300C

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The Central Government imposes the following taxes to fund highways:

• Motor fuel duties and tariffs
• Excise taxes on automobiles, auto components, tyres, etc.
• Excise taxes on grease, oils, etc.

The State Governments levy the following taxes:

• Vehicle registration fees and road tax
• Transport vehicle permits
• Fees for driving permits
• Sales Tax on Car Parts, Tyres, etc.;
• Passenger Tax on Buses;
• Sales Tax on Car Parts;
• Taxes Levied by Local Bodies, Mainly Toll Tax

Since the Central Road Fund (CRF) was established in 1929 through the taxation of motor fuel, this has been the State Government’s primary source of funding for road development without having to again go through the laborious procedure of specific punishments.

However, in recent years, the CRF and general revenue have been combined. In March 1976, the Lok Sabha has approved the Ministry of Transport’s decision confirming the CRF’s existence separately with the predetermined goals. The levy on customs and excise on motor spirit would be set aside in an amount of at least 3.5 pence per litre for the CRF for the construction of roads. When using this fund, initiatives with national significance in India would receive more focus. The federal government would keep 20% of the fund for future use. Additionally, the capital will be used for traffic studies, economic surveys, and plans for young engineers’ training. Approximately Rs. 12,000 Cores in gross revenue came from road transport in India during the sixth plan years of 1978–83 and 1980–85.

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The four forces of shear, compression, tension, and moment are used to categorise different types of bridges based on how they are distributed throughout the bridge’s structure.

In general, there are two types of bridges: regular overpass bridges and unusually designed bridges over rivers, chasms, or estuaries. Due of the unique bridges’ greater technical, economic, and aesthetic interest, this page focuses on describing elements that are common to both types.

A building designed to cross a river, chasm, road, or any other physical obstacle. The design of the bridge is determined by the location in which it will be built and the function that the bridge must perform.

Types of bridges

Bridges can be categorized in several different ways. Common categories include the type of structural elements used, by what they carry, whether they are fixed or movable, and by the materials used.

Structure type

The distribution of tension, compression, bending, torsion, and shear forces inside a bridge’s construction can be used to classify them. All of the major forces will be used by most bridges, but only a handful will be dominant. The division of the forces might be very obvious. In the elements in tension are distinct in arrangement and shape, whether they are suspended or cable-stayed. In other situations, the forces could be divided among a lot of members, such in a truss.

Beam bridges

It consist of horizontal beams that are continuous when they span two or more spans or merely supported when they only link across one span at each end by foundation elements. The intermediate supports, or piers, are used when there are many spans. The earliest beam bridges were rudimentary structures made of logs that crossed waterways. Beam bridges today can be made from either little timber beams or big steel boxes. The shear and flexural stress on the beam caused by the vertical force on the bridge is transmitted throughout its length to the side substructures.

A truss bridge

It is a bridge with a truss as the load-bearing superstructure. This truss is made up of joined components that are arranged in triangle-shaped units. The associated components (usually In reaction to dynamic forces, straight) may experience stress from tension, compression, or perhaps both loads. One of the earliest varieties of contemporary bridges is the truss bridge. The fundamental truss types Bridges in this article have straightforward designs that a nineteenth-century engineer might understand and engineers from the early 20th century. Due to the use of trusses, truss bridge construction is affordable effective material use.

Cantilever bridge

The majority of cantilever bridges employ two continuous spans that meet in the middle of the obstruction they are meant to overcome, extending from the opposing sides of the supporting piers. The materials and construction methods used to build beam bridges are largely the same for cantilever bridges. The forces acting through the bridge make a difference.

Arch bridges

Abutments are found at each end of an arch bridge. The bridge’s weight presses against the abutments on either side. Greek engineers created the Bridge, one of the earliest arch bridges that are known to exist.

Tied arch:

Bridges are similar to ordinary arch bridges in that they have an arch-shaped superstructure. The ends of the arches are held in place by tension in the lower chord of the structure, which prevents the weight of the bridge and traffic loads from acting as thrust forces on the abutments.

Suspension bridge

Bridges that rely on suspension are supported by cables. The oldest suspension bridges were constructed using bamboo pieces to cover ropes or vines. The cables in contemporary bridges dangle from towers that are joined to caissons or cofferdams. The caissons or cofferdams are embedded deeply into the lake, river, or ocean bottom. Simple suspension bridges, stressed ribbon bridges, under spanned suspension bridges, suspended-deck suspension bridges, and self-anchored suspension bridges are some of the subtypes. Additionally, there is a type of bridge that is often referred to as a “semi-suspension,” the Ferry Bridge in Burton-upon-Trent being the only one of its sort in Europe.

Cable-stayed bridge:

Similar to suspension bridges, cable-stayed bridges are supported by cables. Less cable is needed for a cable-stayed bridge, and the towers that carry the cables are proportionately smaller.

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The absolute minimum sight distance (SSD) for the design speed shall be made available along the whole length of the road, regardless of the type of road. If SSD is not available on a stretch of road for whatever reason, such as a visual blockage, prompt action should be made to either clear the impediment from the line of sight or erect signs that state the speed limit and the appropriate warnings.

Overtaking Sight Distance:

On the majority of road lengths, it is ideal to have sufficient overtaking sight distance so that fast moving vehicles can pass slowly moving ones as soon as possible.

• Where overtaking is not restricted, the minimum overtaking distance shall be (d1 + d2 + d3) for road segments with two-way traffic activity.
• On roads with only (d1 + d2) and on divided highways where no traffic is anticipated from the opposing direction.
• It is not necessary to give the standard OSD on split highways with four or more lanes, but the sight distance on any highway should be more than the SSD, which is the bare minimum sight distance.

Overtaking Zones:

It is preferable to build highways so that there is always enough road ahead to allow for safe passing. There may be stretches where the safe overtaking distance cannot be supplied since it is rarely practicable. Before restricted zones begin, sign posts indicating No Passing or Overtaking Prohibited should be put up in areas where overtaking or passing is unsafe or not possible.

However, cars travelling at design speed should be given as many opportunities to overtake as practicable. Overtaking Zones are those areas designated for overtaking.

For safe overtaking, the width of the carriageway and the length of the overtaking zone should be adequate. Sign posts should be placed far enough in front to signal the beginning of the overtaking zones; for one-way roads, this distance may equal (d1 + d2); for two-way roads, it may equal (d1 + d2 + d3).

The overtaking zone must be at least 3 feet long (OSD)

The ideal distance between overtaking zones is 5 (OSD)

Intermediate Sight Distance:

Where required OSD cannot be delivered, alternate Sight Distance ISD equal to double SSD may be provided as far as is practicable. The driver’s eye level and the object’s height can both be assumed to be 1.2 metres above the road surface for calculating the ISD.

ISD = 2 SSD

Sight distance at intersections:

Visibility should be provided for drivers coming from either side of an intersection where two or more roads converge. They ought to be able to recognise a danger and halt their car if necessary. The design speed can be used to calculate the stopping sight distance for each road. The drivers on either side should be able to see one another thanks to the sight distance that should be supplied.

In the image above, this is demonstrated. There are three scenarios in which the sight distance design at crossings may be applied:

• Permitting an oncoming car to alter its speed
• Enabling a halted car to cross a major route
• allowing an approaching vehicle to stop

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The following are the suppositions used to determine the values of d1, d2, and d3 (m):

• Until there is a chance for a safe overtaking operation, the overtaking vehicle A is compelled to slow down from its design speed of v (m/sec) to Vb (m/sec) of the slow vehicle B and move behind it, leaving a spacing of s (m).
• The vehicle A goes at a speed of vb (m/sec) via a distance of d1 from position A1 to A2 when the driver of vehicle A detects a sufficient clear gap ahead and decides within a response time t (sec) to accelerate and pass the vehicle B.
• In the time T (sec) between positions A2 and A3, the vehicle A accelerates and passes the slower vehicle B within a distance d2. The distance d2 is divided into three pieces.

• The distance travelled by the slow vehicle B between B1 and B2 during the overtaking manoeuvre of A;
•  The spacing, s (m), between A2 and B1 The vehicle C approaching from the opposite direction moves over a distance of d3 from position C1 to C2 during this overtaking period T (sec).
• Spacing (m) between B2 and A3.

Determination of the components of OSD

• From point A1 to A2, the distance, d1, travelled by vehicle A after passing it at a slower speed, vb, during the reaction time, t, is equal to vb t. (m). The IRC advises that as the driver’s primary goal is to locate an opportunity to overtake, the reaction time t may be considered as an average value of 2.0 sec. As a result, d1 = 2vb.
• In position A3, ahead of B, vehicle A accelerates from position A2, moves to the next lane, passes vehicle B, and then returns to its original lane during the overtaking time, T. (sec). The straight line between positions A2 and A3 is calculated as d2 (m), which is then divided into three components, d2 = (s + b + s).
• The minimal separation s (m) between the two vehicles while driving at the speed vb (m/sec) may be determined as the minimum distance between positions A2 and B1. The empirical formula s = (0.7 vb + 6) determines the minimal distance between vehicles in relation to their speed.
• The time T now depends on the speed of the overtaking vehicle B and its average acceleration (m/sec2), a. By applying the basic formula for the distance travelled by a uniformly accelerating body with beginning speed vb m/sec and an is the average acceleration during overtaking in m/sec2, d2 = (vb T + 2s), it is possible to compute the overtaking time T (sec).
• When vehicle A is being overtaken, or during time T (sec), the distance travelled by vehicle C driving at design speed v (m/sec) equals the distance d2 (m) between positions C1 and C2.Thus, d3 = v T. (m)In units of m/sec.

OSD = (d1 + d2 + d3) = (vb t + vb T + 2s + vT)

Here, vb = initial speed of overtaking vehicle, m/s

t = reaction time of driver = 2 sec

V = speed of overtaking vehicle or design speed, kmph

T = √4s/A

s = spacing of vehicles = (0.7 vb + 6)

a= average acceleration during overtaking, m/sec.

In kmph units

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Over Taking Requirement and Factors governing the distance:

Theoretically, there shouldn’t need to be any overtaking if every vehicle travels down a road at the intended pace. Each driver is free to travel at lesser speeds, therefore all vehicles actually don’t move at the planned speed. This is especially true when there is mixed traffic. Fast moving traffic must be passed or overtaken in order to proceed. The Minimum Overtaking Sight Distance (OSD) or Safe Passing Sight Distance is the shortest distance that the driver of a vehicle must see in order to safely pass a slow-moving vehicle in front of them.

The OSD is the distance measured along the centre line of the road which a driver with his eye level at 1.2m above the road surface can see the top of an object 1.2m above the road surface.

Factors Affecting OSD:

• The velocities of the vehicles being passed, being passed, and the vehicles coming from the opposite direction
• The distance between vehicles that are being passed and those that are being overtaken; the minimum distance depends on the speeds Road gradient, overtaking vehicle’s rate of acceleration, and the driver’s skill and reaction time.

Analysis of OSD on a Two – Way Road:

Simple overtaking process on a 2 – lane highway with 2 – way traffic movement

Vehicle A wants to pass another slow-moving vehicle B going at a speed of vb m/sec or Vb kmph while travelling at its design speed of v m/sec or V kmph. Before oncoming vehicle C approaches the overtaking stretch, vehicle A must speed, change to the adjacent right-side lane, complete the overtaking manoeuvre, and then return to the left lane.

The overtaking manoeuvre may be split up into 3 operations, thus dividing OSD into 3 parts d1, d2and d3.

• d1 is the distance (m) travelled by the overtaking vehicle A during the reaction time, t (secs) of the driver from position A1 to A2 before starting to overtake the slow vehicle B
• d2 is the distance travelled (m) travelled by the vehicle A during the actual overtaking operation during T (secs) from position A2 to A3
• d3 is the distance (m) travelled by oncoming vehicle C during the actual overtaking operation of A during T (secs) from position C1 to C2. Thus, on a 2-lane road with 2-way traffic the OSD = d1 + d2 + d3 in meters

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The Karnataka State Highways Improvement Project (KSHIP):

• The World Bank is supporting a project by the Karnataka government’s Public Works Department to upgrade the state’s road system.
• In 1996, the Public Works Department conducted a Strategic Option Study (SOS) on a network of 13,362 km of roads, including State Highways and Major District Roads. The study selected 2888 km of roads that should receive priority enhancements.
• The Department of Economic Affairs of the Ministry of Finance, Government of India, has accepted Project Coordinating Consultancy (PCC) Services from the World Bank to investigate and prepare a detailed project report on the 2888 kms and Institutional Development Strategy (IDS) Study. This loan for technical assistance (T.A.) is worth US$3.2 million.
• Eight contract packages, with contract values ranging from Rs. 35 crores to Rs. 205 crores, would be used to carry out the work related to upgrading and widening of 992 Km under International Competitive Bidding (ICB).
• National Competitive Bidding will be used to buy rehabilitation and upgrade contracts with smaller values, ranging from Rs. 3 crore to Rs. 38 crore (NCB).

Karnataka Road Development Corporation Limited (KRDCL):

• In accordance with the provisions of the Company’s Act of 1956, it was established as a fully owned government of Karnataka company on July 21, 1999.
• The Department of Public Works, Ports, and Inland Water Transport oversees KRDCL. This company was founded to promote surface infrastructure by undertaking road works, bridge construction, etc., to improve the road network by undertaking road widening and strengthening, bridge construction, road maintenance, etc., and to take up projects on BOT, BOOT. Karnataka Road Development Corporation Limited has worked to establish connectivity to all nooks and crannies of the State ever since it was founded.

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Pradhan Mantri Gram Sadak Yojana (PMGSY):

• On December 25, 2000, the Indian government announced its debut.
• The goal was to build all-weather roads that would connect all unconnected settlements with a population of 500 or more.
• The barrier is lowered for tribal areas, hills, and deserts, as well as any settlements with a population of more than 250. Implementing this programme is the responsibility of the Ministry of Rural Development (MoRD). This initiative is managed and supported technically by the National Rural Development Agency (NRRDA), a division of the Ministry.
• With the help of the Indian Roads Congress, the Ministry of Rural Development has already released Standard Data Book and specifications specifically for rural roads. This has aided in the establishment of national guidelines and standards for rural roads at the federal level for uniform implementation at the local level while properly taking into account the various topographies, soil types, and traffic patterns across the nation.
• The phrase “village connectivity programme” is commonly used.
• According to estimates, the PMGSY programme will require the construction of roughly 1.79 lakh disconnected habitations.
• This would include 3,75,000 km of new construction at an estimated cost of Rs. 78,000 crore and 3,72,000 km of renovations at an estimated cost of Rs. 59,000 crore.

National Highways Development Project (NHDP):

The National Highways Authority of India Act, 1988, a piece of parliamentary legislation, established the National Highways Authority of India.

The National Highways Development Project (NHDP)

• Which is India’s largest-ever highways project
• World-class roads with uninterrupted traffic flow, is implemented by NHAI.

It is responsible for the development, maintenance, and management of National Highways.

Through the various phases of the National Highways Development Project (NHDP), which are briefly described here, the Government of India has started significant endeavours to enhance and reinforce National Highways.

• NHDP Stage I: The Golden Quadrilateral (5,846 km), the NS-EW Corridor (981 km), port connection (356 km), and other projects make up the majority of NHDP Phase I, which the Cabinet Committee on Economic Affairs (CCEA) authorised in December 2000 at an estimated cost of Rs. 30,000 crore (315 km).
• NHDP Phase II: The NHDP Phase II, which totals 6,647 km in length and was approved by CCEA in December 2003 at an estimated cost of Rs. 34,339 crore (2002 prices), consists mostly of the NS-EW Corridor (6,161 km) and additional National Highways of 486 km length. Phase II is 6,647 kilometres long in total.
• NHDP Phase-III: On September 3, 2005, the government gave the go-ahead for the anticipated expenditure of Rs. 22,207 crores to upgrade and four-lane 4,035 km of national highways on a BOT basis (2004 prices).At an estimated cost of Rs. 54,339 crores, the government approved upgrading and installing 4 lanes on 8074 km in April 2007.
• NHDP Phase IV: On October 5, 2006, CCEA approved repaving 6,500 km of existing four-lane highways as part of NHDP Phase V. (on DBFO basis). 5,700 km of the Golden Quadrilateral and other parts are included in the 6,500 km six-laning.
• NHDP Phase V: The CCEA approved 1000 km of expressways in November 2006 at an estimated cost of Rs. 16680 crores.
• NHDP Phase VI: The CCEA approved 700 km of Ring Roads, Bypasses, and Flyovers as well as a few chosen segments in December 2007 for an estimated cost of Rs. 16680 crores.

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Salient Features of Fourth Twenty Year Road Development Plan:

• The Road Development Plan Vision: 2021, which was created with the full participation of the highway profession in both the public and private sectors, expresses the intention for highway development in the 20 years starting in 2001.
• This vision addressed issues such as the need to mobilise financial resources, including the expansion of the road fund, toll financing, private sector participation, capacity expansion of main highways, pavement strengthening to handle the movement of heavy commercial vehicles, undertaking a massive programme of village road construction, and preservation of existing road assets.
• Needs for road construction in the North Eastern region and other remote places have received specific attention in the aforementioned document.
• Using the most cutting-edge and sophisticated tools for building roads was given priority.
• The importance of research and development efforts in the road sector has increased.
• Priority was placed on improving road safety through various engineering techniques.
• More focus should be paid to engineer training.
• Providing complete connectivity to all habitations, including the construction of bridges and culverts, must be the goal. The following concept for new connectivity has been suggested as a result.
• Habitations with populations above 1000 by the year 2009–10 (or 500 in the case of hills, NE states, deserts, and tribal areas) and above 500 by the year 2014–15 (or 250 in the case of hills, NE states, deserts, and tribal territories) Communities with a population of more than 250 by 2021–2022.

The following list provides the country’s 2020 primary and secondary road system total target lengths:

a. The main highway network

• 15,766 km of expressways (Target length)
• 80,000 km (target length) of national highways; 57,700 km (Achieved length)

b. Secondary road network:

• 1,60,000 km (target length) of State Highways; 1,24,300 km (Achieved length)
• 3,20,000 km (target length) of major district roads; 29,94,000 km (Achieved length)
• Other District Roads and Village Roads: 29,94,000 km (achieved length), no objective set.

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