highway and railroad engg chapt 1-4

Transportation

is a way of movement of human beings and goods from one place to another.

Earthen roads

are laid with soil. They are cheaper than all types of roads. This type of road is provided for fewer traffic areas or countryside areas.

Gravel roads

are also low-quality roads, but they are better when compared with earthen roads.

Murrum

is a matter obtained from the disintegration of igneous rocks by weathering agencies.

Kankar

is an impure form of limestone. These roads are provided where lime is available in a reasonable quantity. These roads are low quality and performance.

Water Bound Macadam

roads contain crushed stone aggregate in its base course. The aggregates are spread on the surface and rolled after sprinkling water.

Bituminous roads

are prevalent roads around the world. They are the most used roads in the world. This road types are low in cost and suitable for driving conditions. The thickness of these roads depends upon the subgrade soil conditions.

Cement concrete

is used to construct the pavements in case of concrete roads. These are very popular and costlier than all other types of roads. They are not flexible, so they require less maintenance.

National Highways

are the main roads that connect all major cities to the capital of the country. They run throughout the length and breadth of the country.

State Highways

are the second main roads that connect significant parts of the state within it. It ultimately connects to the national highways.

District roads

are provided within the cities and connect markets and production places to state and national highways.

Major district roads

It connects headquarters of the neighboring district with main parts of the area.

Minor district roads

are laid within the region.

Village roads

connect the nearby villages. They lead to a nearby town or district roads. Usually, low-quality roads are provided because of low traffic.

light traffic roads

The roads which are carrying 400 vehicles daily on an average is called _________.

medium traffic road

If a road is carrying 400 to 1000 vehicles per day, then it is said to be a _________.

high traffic road

If a road is carrying is more than 1000 vehicles per day then it is considered as _____________.

Pedestrian ways

are exclusively built for pedestrians, and no vehicles are permitted in this way.

Cycle tracks

are provided on both sides of the pavement for cyclists; hence they can travel safely.

Motorways

are also known as expressways. Only a few vehicles are accessible to use this type of road. The cars which can move with high-speed acceleration are permitted in this way.

Flexible roads

It consists of a flexible layer as a pavement surface, which requires proper maintenance; otherwise, it can be disintegrated easily with heavy traffic.

Rigid pavements

are non-flexible and cement concrete roads are fall under this category.

plain area roads

The roads constructed on leveled surface is known as

hilly area roads

Roads constructed in hilly regions. Generally, these are provided around the hill in a spiral shape.

RECTANGULAR OR BLOCK PATTERN

In this type of road pattern, the complete area is divided into rectangle or block-shaped plots to create a rectangle or block pattern.

RADIAL PATTERN

In this road pattern, the network of roadways is constructed in the shape of a circle that radiates away from the center of the area.

RADIAL OR STAR AND BLOCK PATTERN

The entire area is divided into a radial network of roads radiating from the center outwardly with a block pattern network of roads in between the radial main streets

RADIAL OR STAR AND CIRCULAR PATTERN

It is a road pattern in which the major roadways, or radial roads, radiate outward from the center and are joined by the ring roads, or concentric roads, which likewise radiate outward

RADIAL OR STAR AND GRID PATTERN

From the center, a radial network of roads radiates outward. The grid pattern is then used to interconnect the main radial streets.

HEXAGONAL PATTERN

is a network of roadways that form a hexagonal shape, similar to a circular road pattern. Three roads intersect with the constructed region at each corner of the hexagon.

minimum travel pattern

the road pattern grows linearly in one direction possible (straight roads)

GRID PATTERN

A network of intersecting parallel lines, real or imaginary, is referred to as a grid. When seen from above, this pattern is made up of streets that connect at right angles to form squares.

LINEAR PATTERN

It comprises a road that expands linearly in one direction, potentially due to certain natural resources like the sea or ocean existing on one side of the city

ECONOMIC STUDIES

Details the existing facilities, their utility, distribution of the existing population in the area, population growth trends, existing products in the agricultural and industrial sectors

FINANCIAL STUDIES

Various financial aspects such as the sources of funding, estimated revenue from taxes on vehicles, and toll tax.

TRAFFIC / 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

ENGINEERING STUDIES

These include study of the topography, soil, road life and special problems, if any, relating to construction, drainage, and maintenance.

HIGHWAY ALIGNMENT

A crucial aspect of highway and railroad engineering, as it determines how roads and railways will be constructed and maintained

DIRECTNESS / SHORT

The aligned route between end points should be as direct as possible and result in the minimum possible length under the circumstances.

EASY

The alignment should be such that it is easy to construct, maintain and operate the highway. The curves and gradients should be easy.

SAFE

Safety for the road-users should be the primary consideration; the stability of natural slopes and man-made slopes for embarkments and cuttings should be ensured to prevent possible accidents.

ECONOMICAL

The overall cost of construction and maintenance of the road, as also the operation cost of the vehicles should be as low as possible

special considerations

Depending upon the purpose of the highway and the characteristics of the terrain, this may be needed as in the case of hill roads or ghat roads

GEOLOGY

The type of rock and soil in the area can affect the stability of the highway.

POSITIVE POINTS

These are those points through which the alignment should pass

NEGATIVE POINTS

These are those points through which the alignment should not pass

POSITIVE POINTS

what type of obligatory point is Existing Road

POSITIVE POINTS

what type of obligatory point is Intermediate Town

POSITIVE POINTS

what type of obligatory point is Bridge Site/Existing Bridge

POSITIVE POINTS

what type of obligatory point is Mountain

NEGATIVE POINTS

what type of obligatory point is Valleys, ponds, and marshy land

NEGATIVE POINTS

what type of obligatory point is Religious places

NEGATIVE POINTS

what type of obligatory point is Conservation areas and restricted zones.

NEGATIVE POINTS

what type of obligatory point is the Densely populated area

AVAILABILITY OF MATERIALS AND LABOR

The construction works become easier and economical when the construction materials are near the place of highway alignment

ECONOMIC CONSIDERATIONS

The construction, operation, and maintenance work should be economical. So, highway alignment is selected keeping these things in mind.

POLITICAL CONSIDERATIONS

The pressure from the government to run the highway alignment in the way they decide also affects the selection of highway alignment.

DRAINAGE

The alignment needs to be fixed such that the number of cross drainage structures are less.

MONOTONY

Setting the straight alignment leads to monotonous driving. The roads are designed as forgiving roads.

TRAFFIC

The alignment should be according to the traffic amount and flow pattern.

SIGHT DISTANCE

The safe and efficient operation of vehicles on roads depends very much on the visibility of the road ahead of the driver.

SIMPLE CIRCULAR CURVE

is a type of curve that are the most common and easiest to construct, as they require minimal earthwork and can be built quickly. However, they can also lead to driver fatigue and boredom, which can increase the risk of accidents. are typically used for highways with high traffic volumes and low accident rates

COMPOUND CURVE

a type of curve that offer more visual interest and can help keep drivers alert. However, they require more earthwork and can be more difficult to build. are better suited for highways with lower traffic volumes and higher accident rate

SPIRAL CURVE

are a combination of straight and compound curves, offering both visual interest and ease of construction. They are often used in mountainous terrain where space is limited and steep grades are necessary. are often used in areas with limited space or challenging topography

1. Computer Aided Design (CAD)

2. Global Positioning System (GPS)

3. Aerial photogrammetry

4. Point Cloud Modeling

TECHNOLOGies USED IN HIGHWAY SURVEYING

MAP STUDY

A preliminary study of the geographical area and land topography is done by analyzing maps in detail. It provides engineers with the various artificial and natural features regarding a particular location

RECONNAISSANCE SURVEY

This study is performed as an intersection based on the map study. The routes analyzed through surveying, if found impossible, are excluded from the map plan. In the end, engineers are left with information and routes which can be analyzed and carried forward in the next phase.

PRELIMINARY SURVEY

In this phase of the survey, the data and the routes which are acquired through the rough survey are further processed and surveyed in depth. All the data are collected and analyzed in detail, A best alignment and construction plan is finally decided

Traverse

-is run from the starting point to the end point by setting out various control points.

Levelling Work

-is carried out along the center line or the proposed road. This is used to estimate the volume of the earthwork.

Topographical Features

all geographical and man-made features are survey and plotted which are along the traverse and for a certain width on either side.

Drainage Studies and Hydrological Data

-the number of cross drainage structures are estimated during the preliminary survey.

Soil Survey

is conducted in working out details of earthwork, slope, and stability of materials, subsoil and surface drainage requirements and the type of the pavement requirements.

Material Survey

-the location of construction materials needs to be known

Traffic Survey

-survey regarding the number of lanes, roadway width, and pavement design need to be done

Determination of Final Centre Line

-after completion of all the above mention steps and calculating the amount of earthwork, the final centre line is determined.

LOCATION SURVEY

In this phase, all the data collected in the previous phases, are assembled in the form of a construction project document. This documents the precise data points, images, 3d models, drawings, and sketches of the geographical area which will initiate the start of construction project

DETAILED SURVEY

Temporary Bench Marks (TBM) are fixed at all under pass structures and drainage structures. Levels along the final centre line should be taken with great importance as these data are required for vertical alignment, earth work calculation, and drainage details.

Roadways

are a network of roads, highways, and streets that are designed for the movement of cars, trucks, and other vehicles. they are usually owned and maintained by the government and are open to the public for use. They are often used for short-distance travel and for transporting goods.

Railways

are a network of trains and train tracks that are used for the transportation of people and goods over long distances.

Geometric design

in highways refers to the process of planning and designing the physical layout and features of a roadway to ensure safe, efficient, and comfortable travel for motorists. It involves making decisions about the highway's alignment (horizontal and vertical), cross-section, sight distance, and other geometric elements.

Lane Width

the width of the road from the marked centerline to the edge marking if present or the edge of the road surfacing material.

Curve Radii

the curvature of the road

Lane count

is a crucial factor in road design as it determines how many separate paths or lanes are available for vehicles to travel in the same direction. It directly impacts traffic capacity, congestion management, and road safety.

Stopping Sight Distance (SSD)

is the minimum distance required for a vehicle to come to a safe stop without colliding with any obstacles.

Overtaking Sight Distance (OSD)

is the minimum distance needed for a driver to safely overtake a slower-moving vehicle, considering oncoming traffic.

Driver's Reaction Time

The time it takes for a driver to perceive an obstacle and react by applying the brakes is called the ____

Grade

refers to the incline or decline of a road concerning the horizontal plane. It is expressed as a percentage or ratio and indicates how steep or flat a section of road is.

Ruling gradient

is the maximum allowable slope on a road or railway track, expressed as a percentage, to ensure safe and efficient transportation operations.

Limiting gradient

is the maximum gradient steeper than ruling gradient, which may be used in restricted length, where providing a ruling gradient is not possible.

Exceptional gradient

is steeper than the limiting gradient, which may be used only in exceptional situations.

minimum gradient

is done in the longitudinal direction of the road for drainage purposes. There should be a _________ in the drainage for the flow of water.

Superelevation

also known as banking, is the tilting or sloping of a road or a curve on a road to help vehicles navigate it safely at higher speeds. It prevents vehicles from skidding outward when going around a curve by tilting the road surface. This design feature is common on highways and racetracks to improve vehicle stability while turning.

Highway alignment

refers to the position of the central line of a roadway or the planned layout of the road on the ground.

Concrete Barrier

These are heavy, rigid barriers often used in medians to prevent crossover accidents. They are effective at stopping vehicles but can be unforgiving in collisions.

Crash cushions and attenuators

are designed to absorb and dissipate the energy of a collision, reducing the force experienced by vehicle occupants. They are often used in high-traffic areas where the risk of rear-end collisions is higher.

Metal Barriers

These are typically made of steel and offer a balance between strength and flexibility.

Cable Barriers

These barriers consist of steel cables tensioned between posts. They absorb energy during a collision and are often used in medians where space is limited.

Energy-Absorbing Terminals

These are designed to gradually decelerate a vehicle upon impact, reducing the severity of the collision.

Flare End Sections

These provide a gradual transition from the barrier to the roadway, reducing the risk of vehicle snagging or rollovers.