unit-iii-station-yards-railway-signalling-interlocking-railway-track-construction-r-bhagat-2020.ppt

Transportation Engineering-II
Prof. Rajesh Bhagat
Asst. Professor, CED, YCCE, Nagpur
B. E. (Civil Engg.) M. Tech. (Enviro. Engg.)
GCOE, Amravati VNIT, Nagpur
Achievement
 Selected Scientist, NEERI-CSIR, Govt. of India.
 GATE Qualified Three Times.
 UGC - NET Qualified in First Attempt.
 Selected Junior Engineer, ZP Washim.
 Three Times Selected as UGC Approved Assistant Professor.
 Assistant Professor, PCE, Nagpur.
 Assistant Professor, Cummins College of Engg. For Women.
 Topper of PhD Course Work at UGC-HRDC, RTMNU Nagpur.
Mobile No.:- 8483002277 / 8483003474 Email ID :- rajeysh7bhagat@gmail.com
Website:- www.rajeysh7bhagat.wordpress.com

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Course Objective:
1) To acquaint development of railway transportation in India.
2) To understand geometric design of railway tracks.
3) To know zoning laws for development of air transportation in India.
4) To study tunnel alignment and necessity of tunnels.
Course Outcome:
1) An ability to update & upgrade knowledge about transportation system in India.
2) An ability to design railway tracks & crossing.
3) An ability to avail information about development of air transportation in urban areas.
4) An ability to understand the construction of tunnel & advances in tunneling.

Unit-I
1) Transportation and Its Development: Long term operative plans for Indian Railways,
Classification Lines and their track standards
2) Railway Terminology
3) Administration & Management
4) Traction and tractive resistance, Hauling capacity and tractive effort of locomotives,
Different types of tractions
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Unit-II
1) Permanent Way: Alignment surveys, requirement, gauges, track section, coning of
wheels, stresses in railway track, high speed track, rail types and functions, selection
for rails, test on rail wear & defects, corrugation and creep of rails, rail joints, short and
long welded panels.
2) Sleepers: Function, types, merits and demerits, sleeper density, ballast cushion, ballast
section, rail fixtures and fasteners.
3) Geometric Design of Railway Track: Gauge, gradients, speed, super elevation, cant
deficiency negative super elevation, curves, length of transition curves, grade
compensation.
4) Points and Crossing: Left and right hand turnouts, turnouts & crossovers, railway track
functions .

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Unit-III
1) Station and Yards: Types, functions, facilities & equipments.
2) Railway Signaling and Interlocking: Objects and principles of signaling, classification
and types of signals, control and movement of trains, track circulation, interlocking.
3) Railway Track construction, inspection & modern techniques of maintenance, modern
technology related to track & tractions, rolling stock, signaling & controlling

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Unit-IV
1) History of Air Transportation in India: Comparison with other transportation modes,
aircraft components and characteristics, airport site selection, modern aircrafts.
2) Airport Obstructions: Zoning laws, imaginary surfaces, approach and turning zone,
clear zone, vertical clearance for highway & railway.
3) Runway And Taxiway Design: Windrose diagram, cross wind component, runway
orientation and configuration, basic runway length and corrections, runway geometric
design standards, taxiway layout and geometric design standards, exit taxiway.

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Unit-V
1) Airport Layout and Classification: Terminal area, aircraft parking and parking systems,
unit terminal concept, aprons, hangers, International airports layout, helipads and
heliports.
2) Visual Aids: Airport marking and lighting for runways, taxiways and other areas.
3) Air Traffic Control: Need, networks, control aids, instrumented landing systems,
advances in air traffic control.

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Unit-VI
Tunnels: Alignment, surveys, cross section of highway & railway tunnels, tunneling
methods in hard rock and soft grounds, tunnel lining, drainage, ventilation and lighting of
tunnels, advances in tunneling techniques, tunnel boring machines, case studies.

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SN Author Name Title Publication
1 S. C. Saxena & S. P. Arora Railway Engineering Dhanpath Rai
2
S. K. Khanna
M. G. Arora
S. S. Jain
Airport Planning and Design Nem Chand & Bro.
3 S. P. Chandola Transportation Engineering S. Chand
4 S. C. Rangwala Railway Engineering Charotar House
5 S. C. Saxena Tunnel Engineering Dhanpath Rai
SN Author Name Title Publication
1. Robert Horonjeff, Francis, et al Planning and Design of Airports The McGraw Hill Co.
Text Books:
Reference Book:

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Railway Station:
1) A railway station or a railroad station and often shortened to just station.
2) A place where trains regularly stop to load or unload passengers and goods.
3) A place where railway trains come to halt on order to take up and get down passenger and
goods.
4) At station traffic is booked and an authority is given to travel in the trains.

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Purpose of Railway Station:-
1) To take up or exchange of passengers and goods.
2) To control the train movements
3) To enable the trains on a single line track , to cross from opposite directions.
4) To enable the following express trains to overtake
5) For taking diesel or coal and water for locomotives
6) For detaching engines and running staff
7) For detaching or attaching of compartments and wagons
8) For sorting of bogies to form new trains, housing of locomotive in loco sheds.
9) In emergencies in ease of dislocation of track due to rains, accidents etc...
10) For repairing engines and changing their direction

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Requirements of Railway Station:-
A railway should satisfy the following basic requirements provided for:
1) Public
2) Traffic Staff & Police
3) Trains Requirements
4) Locomotives
5) Development of Railways:

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Public Requirements:
1) A booking office for tickets.
2) Good & Passenger platforms.
3) Drinking Water.
4) Lighting & Ventilation.
5) Waiting Room.
6) Sanitary Arrangements
7) Telephone, Refreshment Room, Inquiry room, etc
8) Display Board
Traffic Staff & Police:
A station should provide facilities to staff to perform their duties in a best possible way

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Trains Requirements:
1) Control of movements by signal.
2) Sufficient number if sidings & platforms.
Locomotives:
1) Proper arrangement for supply of fuel and water to locomotives.
2) Arrangement for cleaning, examining, inspection & maintenance.
Development of Railways:
1) Easy & comfortable approach road to station.
2) Installation of clock for correct time, guide map of city & display boards.
3) Availabilities of coolies.
4) Waiting rooms, underground passages, staircase, escalators, restaurants, etc.

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Factors Influencing The Selection of Site for a Railway Station:
1) Close to town.
2) Sufficient area availability for future development.
3) Fairly level ground.
4) Road connectivity.
5) Site should not be on the curve of railway line.
6) Sufficient quantity of water.
7) Should not be in low laying area.
8) Site should not be on slope.
9) Drainage facilities.

Classifications of Railway Stations
Railway stations
Operational
Block Non-Block
3.Class C
2.Class B
1.Class A 1.Class D
2.Flag
3.Spl.class
Functional
1. Wayside
2.Junction
3.Terminal

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Station can be classified according to operational & functional characteristics as below:
A) Operational Classification: Indian Railway classified the stations as below.
1) Block Stations – Class A, Class B, & Class C in descending order of importance.
2) Non-block Stations – Class D Stations & Flag Stations.
3) Special Class Stations.
B) Functional Classification: Based on their function, stations are classified as below.
1) Wayside Stations
2) Junction Stations
3) Terminal Stations

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A) Operational Classification:
1) Block Stations – Class A, Class B, & Class C in descending order of importance.
 Block station is a place on the railway line at which permission to approach
and authority to proceed are granted.
 Block stations are sort of compartments into which the rail line is divided, are
established so as to safety space the train behind each other.
 Block stations are made at the ends of block section and are equipped with
signals which demarcate the limits of the block sections.
2) Non-block Stations – Class D Stations & Flag Stations.
 These are called Class D or Flag stations.
 These are situated between two consecutive block stations
 They do not define the boundary of any block section.
 Neither telegraphically connected to adjacent stations nor have any apparatus
or staff for controlling the movements of train.
3) Special Class Stations – Those are not covered under A, B, C, & D classes

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Class A Stations: Where the line has to be cleared up to an adequate distance (400m)
beyond the home signal for giving permission to approach to a train.
Home Signal, Starter Signal & Warner Signal.
Class B Stations: Where the line has to be cleared upto an adequate distance beyond the
outer signal before giving permission to approach to a train. Outer signal is used at
distance of 580m from the home signal.
Class C Stations: It is a block hut where no passenger are booked. It is used as a means to
split a long block section so that the interval between successive trains is reduced. Trains
usually do not stop at these stations.
Class D Stations: Station does not define the boundary of any block section. No staff for
controlling movements of the trains.
Flag Stations: Trains are stopped by various ad hoc arrangements. Not connected
telegraphically & no apparatus.
Special Class Stations: Those are not covered under A, B, C, & D classes.

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Functional Classification: Based on their function, stations are classified as below.
1) Wayside Stations
2) Junction Stations
3) Terminal Stations
Wayside Stations:
 In this type arrangements are made for crossing or for overtaking trains.
 Wayside stations are of the following types.
 Trains move only in two direction i.e. up & down side direction.

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Junction Stations:
 At a junction stations, lines from three or more directions meet.
 The stations where a branch line meets the main line are known as junctions.
 Facilities for interchange of traffic between main and branch line
 Facilities to clean and repair the compartments of the trains
 Facilities for good sidings, engine sheds, turn table etc.

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Terminal Stations:
 It is a station where a railway line or one of its branches terminates.
 Watering, coaling, cleaning, servicing the engine.
 Turn table for the change of direction of the engine.
 Facilities for dealing goods traffic.
 Marshalling yard, engine sheds, sidings etc.
 Ticket office, restaurant etc are provided and it is directly connected to the road.

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Platforms :
1) A section of pathway, alongside rail tracks at a railway station.
2) A place at which passengers may board or alight from trains.
3) Larger stations having multiple platforms.
4) Platform types include the bay platform, side platform & island platform.
5) A bay platform is one at which the track terminates, i.e. a dead-end or siding.
6) A side platform is the more usual type, alongside tracks where the train arrives from
one end and leaves towards the other.
7) An island platform has through platforms on both sides; it may be indented on one or
both ends, with bay platforms.

Passenger Platform & Goods Platform
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Requirements of Platforms :
The sills of wagon doors of trains are considerably higher than the rail level. Therefore for
entering and getting down of passenger & for loading & unloading of goods from trains,
suitable surface known as platform are required.
1) Minimum length of platform should be 180m.
2) Minimum width of platform should be 3.67m & should be paved fully.
3) Platform should be covered atleast for a length of 60m.
4) Drinking water & sanitary facilities must be provided.
5) Sign boards.
6) Ventilation & Lighting arrangements.
7) Slope of platform in its width should be 1 in 30.

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Passenger Platforms:
 Passenger enters & get down the train are called passenger platforms.
 Minimum paved width should be 3.67m.
 Drinking water, lighting, etc. facilities.
 Boards or sign boards.
Goods Platform :
 Goods are dispatched or dislodged.
 Height of these platform are kept more.
 Minimum width of platform is 3m.
 Goods shed should be provided.
 Arrangements for weighing the goods.
 Drainage facilities.

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Loop:
1) When a branch line from a main line again terminates at the same main line, it is called
a Loop.
2)Three types of loops: Split Turn Out, Trailing Turn Out & Straight & Loop
3)A straight & loop arrangement is suitable for fast through train as there is no reduction
in speed

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Yard: (Station Yard)
 A system of tracks laid within definite limits for various purposes such as receiving
sorting and dispatch of vehicles on a railway station.
 Yards are provided at the important railway stations such as junction stations, terminal
station, etc.
 To receive, store, clean, repair, sort, make up trains, dispatch train & other purposes.
 Movements of trains is controlled by prescribed rules, regulations & signals provided
separately for yards.

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Types of Yards:
 Passenger yards
 Goods yards
 Marshalling yards
 Locomotiveyards

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Passenger Yards:
Function of passenger yard is to provide all the facilities for the safe movement of
passengers.
Facilities in passenger yards:
1) Booking office, enquiry office, luggage booking room, and waiting room for
passengers.
2) Parking space for vehicles.
3) Signals for reception and dispatch of trains.
4) sidings for shunting facilities.
5) Facilities for changing batteries.
6) Facilities for passing a through train.
7) Washing lines facilities.

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Goods Yard:-
1) Provided for receiving, loading and unloading of goods from wagons.
2) Goods yard also known as a goods station or goods depot.
3) It may be paved with gravel, moorum, WBM, bituminous pavement & concrete
pavement.
4) It is widest sense, a railway station which is exclusively used to load & unload goods
from ships or road vehicles and/or where goods wagons are transferred to local
sidings.
Requirements of Goods Yard:
1) Approach road for movement of goods.
2) Sufficient number of platforms for loading & unloading.
3) Sufficient number ofgodowns.
4) Bookingoffice.
5) Cart weighing machine.
6) Cranes for loading & unloading.

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Marshalling Yards:-
1) Place where goods wagons received from different centres are sorted out & placed in
order to be detached at different station.
2) The marshalling yards are distribution centres.
3) Empty wagons are also kept in marshalling yards.
4) It is centre where goods wagons are sorted out & isolated wagons are combined to form
a train load.

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Factors For the Efficient Functioning of Marshalling Yards:-
1) Shunting operations should not disturb the regular trains.
2) Should be kept parallel to the runningtrains.
3) Movement of wagons in one direction only.
4) Repair facilities should be provided on one ormore sidings.
5) Connected to all important railway stations.
6) Goods yard should be nearer to the marshalling yard.

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Types of Marshalling Yards:-
1) Flat yard: Flat yards are constructed on flat ground, or on a gentle slope. A flat yard
has no hump, and relies on locomotives for all car movements
2) Gravity yard: The whole yard is set up on a continuous falling gradient and there is
less use of shunting engines. Very large capacity but they need more staff than hump
yards and thus they are the most uneconomical .
3) Hump yard: These are the largest and most effective yards, with the largest shunting
capacity—often several thousand cars a day. The heart of these yards is the hump. A
hump yard has a constructed hill, over which freight cars are shoved by yard
locomotives, and then gravity is used to propel the cars to various sorting tracks

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Locomotive Yards:-
1) This is the yard which houses the locomotives for various facilities such as watering,
fueling, cleaning, repairing, servicing etc.
 Should be located near the passenger and goods yards.
 Water column, Engine shed, Ash pit, inspection pit, repair shed, turn table.
 Hydraulic jack for lifting operations.
 Place for future expansion.

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Reception Siding:-
1) Used to receive the incoming trains. The incoming trains stand on theses sidings and
wait for their turn of shunting operations.
2) The shunting are generally laid in the form of a grid and their lengths kept equal.
Sorting Siding:-
1) Used during shunting operations.
2) Each siding is allotted to wagons bund for one particular direction or destination.

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Station Equipments:-
For efficient running of trains, safety of traffic, repairing, cleaning, examining of
locomotives etc. some equipments and machinery are needed. These equipments are
known as station equipment.
Engine Shed, Water Column, Ash Pit,
Turn Table, Triangle, Buffers Stop,
Fouling Marks, Examination Pits, Traverse,
Derailing Switch, Drop Pits, Scotch Block,
Sand Hump, Weigh Bridge, etc.s

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Engine Sheds:-
1) Railway engine sheds were provided at terminal stations, junctions, and other
locations around the railway.
2) Covered accommodation for servicing locomotives (this could be simple tasks such as
changing brake blocks to more complex task that involved dismantling and repairing
the engine)
3) Types of engine sheds are (i) Rectangular type (ii) Circular type
Rectangular Sheds:-
 In this type of engine shed, two parallel tracks are laid, which meet at one or both the
ends.
 The engine can come from one end and leave the shed in other end.
 They need more space.
 They are widely used in India.

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Circular Type Engine Shed:-
1) This type of shed consists of radiating tracks and a circular structure known as round
house.
2) A turn table is also provided with the help of turn table the incoming locomotive is put
up on the unoccupied track of the shed.
3) Needs less place.
4) Skilled labour is needed for the construction.
Turn Table:-
1) A turntable is a device used to turn locomotive or rolling stock.
2) a large circular platform which is used to turn locomotives and other rolling stock.
3) A well-engineered turntable is designed in such a way that the efforts of only two or
three people are needed to operate the turntable, even when dealing with very large
and heavy locomotives.
4) The reason the turntable was developed was because early steam locomotives were
somewhat difficult to run in reverse.

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Triangles :-
1) Used for turning railway equipment.
2) By performing the railway equivalent of a three point turn, the direction of a
locomotive or railway vehicle can be swapped around, leaving it facing in the direction
from which it came.
3) It consists of three short lengths of tracks laid to form a triangle and connected to each
other by three pairs of points and crossings.
4) Two tracks are laid in curves and third as straight.
5) The engine moves completely round the triangle and its direction is automatically
changed.

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Water Column:-
1) A water column is a device used for delivering a large volume of water into tank.The
device is sometimes also called a water crane.
2) As a steam locomotive consumes large quantities of water, water cranes were a vital
part ofrailway station equipment.
3) They are kept at all main line tracks at a distance of not less than 50 Km.
4) Should not have any obstruction to traffic.
5) Foot valve is provided to regulate the water flow.
6) Height of water column is 442cm.
7) Projection of pipe is about 225 cm.
8) Often situated at the end of a platform.

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Ash Pit:-
1) Ash pits are provided to collect the ashes from the locomotives.
2) They are generally 1.067m deep and length is slightly more than the length of the
locomotive.
3) They rest on masonry or concrete walls and rails are fixed on longitudinal beams
provided at the top of the walls.

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Buffer Stop or Bumper:-
1) Prevent railway vehicles from going past the end of a physical section of track.
2) The design of the buffer stop is dependent in part upon the kind of couplings that the
railway uses.
3) Consists of timber beam 30x13cm section of the level of buffer on vehicles, fixed to the
two vertical rail parts bolted to the track rails on other ends.

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Fouling Marks:-
1) Purpose is to avoid side collision between two trains on adjacent track. (in between
diverging/converging tracking )
2) It should be fixed at the point where the spacing between the tracks begins to reduce
to less than the minimum as specified in schedule of dimension.(i.e. 4.27 Meter track
centre normally)
3) They are made up of stone or concrete blocks and painted in black and white

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Examination Pits:-
1. Similar to ash pits but they are used to examine the engines from underneath.
2. These pits are generally longer and deeper than the ash-pits.
3. Provided in locomotive yards.
Traversers :-
1) Used to shift the position of the vehicles or locomotives sideways.
2) They provide an arrangement of transferring engines and vehicles from one track to
a parallel track.
3) Traversers are preferred to turnouts, cross-overs, etc.
4) It consists of a platform mounted on rollers.
5) Vehicle to be shifted is placed on the traverser and then the traverser is moved
sideways and adjusted to the parallel track where the vehicle is to be placed.

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Derailing Switch:-
1) Ordinary pointswitch.
2) The switch is open in the normal position and is generally provided near the dead end of
the siding.
3) Any vehicle passing over it shall be derailedbecause of break of continuity of rails.
Drop Pit:-
 constructed at right angle to the track to examine and repair or to replace the old
wheels by new ones.
 In these pits the wheels of the locomotives are lowered and the wheels and axles are
taken out with the help of different kinds of jacks

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Scotch Block:-
1) It consists of a block of wood placed on the rail and suitably held and locked in
position.
2) It forms an obstruction to the passage of vehicles and hence it prevents the escape of
vehicle beyond the dead end of the siding.

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Weigh Bridge:-
1) These are level platforms with rails and are connected to the main track.
2) The beam rests on the knife edge and attached to the lever to which loaded wagons
come to the siding to the weigh bridge is fixed.
3) The lever mechanism is activated and weight is indicated.

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Signaling:
1)A system used to control railway traffic safely, essentially to prevent trains from
colliding.
2)Consists of the devices and arrangements by which trains are operated efficiently
and tracks are used to maximum extent, maintaining the safety of the passengers, the
staff and the rolling stock.
3)It includes the use and working of signals, points, block instruments and other
equipments.

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Objective of Signaling:-
1) To provide facilities for the efficient moving of trains.
2) To ensure safety between two or more trains which cross or approach each other's
path.
3) To provide facilities for the maximum utility of the track.
4) To provide facilities for safe and efficient shunting operations.
5) To guide the trains movement during maintenance and the repairs of the track.
6) To safeguard the trains at converging junctions and give directional indications of
diverging junctions.
Types of Signal:-
1) According to function.
2) According to location.
3) Special signals.

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Classification according to function:
a) Stop signals or semaphore type signals
b) Warner signals
c) Disc or groundsignals
d) Coloured light signals

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Stop Signals or Semaphore Type Signals:-
 One of the earliest forms of fixed railway signal is the semaphore.
 These signals display their different indications to train drivers by changing the
angle of inclination of a pivoted 'arm'.
 The stop position is the normal position and it is said to be ON position.
 The arm can be lowered at an angle of 400 to 600 with horizontal and is said to be
OFF position.

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Warner Signals:-
 The warner signal is similar to semaphore signal in shape except a v-notch at free
end, ie. The movable arm is fish tailed as shown.
 The white band is also of v-shape.
 The warner signal is placed on the same post of the semaphore signal 1.8 to 2.1m
below the semaphore signal.
 The warner signal is painted yellow and exhibits yellow or amber colour at night
instead of red colour.

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Shunting Signal:- Disc Signal
1) These signals are used for shunting operations in station yards.
2) They are of the shape of a circular disc with a red band on a white back ground.
3) The disc can revolve in a vertical plane by pulling the lever by hand.
4) Two holes are provided, one for red lamp and the other for the green lamp.
5) When the red band is horizontal or shows red light at night it indicates - STOP
6) When red band is inclined at 450 or shown green light at night indicates - PROCEED

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Colour Light Signal:-
1) Semaphore signals are being replaced by high intensity beam colour light signals both
during day and night.
2) the normal position, it indicate –PROCEED (ie. shows green light)
3) When the section is blocked, it indicates – STOP OR DANGER ( shows red light)
4) In India these signals are used on urban and sub-urban sections with heavy traffic.

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Types of Signal According to Location:-
(i)Reception signals
(a)Outer signal
(b)Homesignal
(ii) Departure signals
(a)Starter
(b)Advance Starter

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Outer Signal:-
1) This is the first stop signal which indicates the entry of the train from block to the
station yard.
2) It should be placed at an adequate distance (0.54 km for BG and 0.4 km for MG)
3) It has one arm but may have a warner signal on the same post nearly 2m below it.
4) In the Stop position the driver must bring his train to a stop at a distance of about 90m
before the outer signal and then proceed to the home signal with caution.
5) If it is in the Proceed position then the driver can take the train at speed, assuming that
home signal is also in the proceed position.

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Home Signal:-
1) Due to its location at the door of station, it is termed as Home signal.
2) The home signal has bracketed arms to indicate which line is to be used.
3) The function of home signal is to protect the sidings already occupied.
4) It is located at not more than 180m from the start of points of switches.
5) Home signals carry as many arms as the number of diverging lines.

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Starter Signal:-
1) It marks the limit up to which trains stopping at a station should come to a stand.
2) The starter is the last stop signal at a station.
3) It controls the movements of the trains when they depart from the stations.
4) No train can leave the station unless the starter signal shows the – PROCEED position
(ie. inclined position)

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Advance Starter Signal:-
1) Besides the starter signal for each of the station lines from which trains starts, an
advance starter may also be provided.
2) The advance starter becomes the last stop signal at the stations where is provided.
3) It is an indication for the train having left the station.

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Special Signal:-
1) Repeater or Co-acting signal:
 When the drivers vision is obstructed by an over bridge between the signals, a signal is
provided with a duplicate arm of smaller size at a suitable position which repeats the
indication of signal head. It is therefore termed as Repeater signal.
 This signal is linked with the main signal and therefore, when the lever is pulled both
signals are lowered simultaneously. Also called as ― Co-acting signal.

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2) Routing Signal:
 When various signals for main and branch lines are fixed on the same vertical post,
they are known as routing signals.
 Generally the signal for the main line is kept at higher level than that for branch line.

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3) Calling-on Signal:
 These consist of small and short arms fixed on the same post below main signals.
 A calling-on signal permits a train to proceed cautiously after the train has been
brought to a halt by the main signal.
 This signals are helpful when repair works are going on.

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4)Miscellaneous Signal:
 Various other devices are used for indicating signals.
 Signals are meant for goods sidings are distinguished by providing rings or writing
capital letter etc.,
 Two crossed bars are put up on the signal which is under repair and it is placed in ON
position.

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Control of Movement of Train:-
It is quite essential that movements of trains on tracks should be safe.
The various systems of controlling the movement of trains are as follows:-
1) One Engine Only
2) Follow Train or Time Interval System
3) Pilot Guard
4) Train staff & Ticket
5) Absolute Block or Space Interval System
6) Automatic Block or Automatic Signalling
7) Centralizing Traffic Control
8) Automatic Train Control

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Automatic Train Control System:- ATC
1) Devices used in ATC system help the engine driver to observe visual signals and in case
of his failure , it reduces speed automatically to stop the train.
2) Devices are two types: Cab signaling & Automatic Stopping Devices.
3) In cab signaling, a variable electric current passing through the running rail is picked
up by the locomotive & translated into color light signal in the cab of locomotive.
4) In Automatic, train control by mechanical or electrical devices which either bring the
train to stop automatically if the signal are not observed by the driver or reduces speed
initially and if driver does not respond, then it stops the train automatically.

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Absolute Block System :-
1) The principle of the absolute block system of railway signaling is to ensure the safe
operation of a railway by allowing only one train to occupy a defined section of track at
a time.
2) Instead of a fixed interval of time between successive trains, a varying interval may be
kept depending on the time, actually taken by particular trains.
3) It is a space interval system rather than a fixed interval system.
4) The line is assumed to be blocked until the fact that the line is clear is established by
some suitable information conveyed by block instruments.
5) The electric telegraph provided the ability for signalmen to communicate with each
other and provided the basis for the absolute block system.

73
Pilot Guard System:-
1) Used on certain occasions such as breakdown of telephone and telegraph system.
2) A pilot proceeds by one train to the station ahead and then he returns by a train
running in the opposite direction.

Centralized Traffic Control (CTC):-
1) It is a form of railway signaling that originated in North America.
2) Train movements are decided by signals only, which are controlled over a
considerable length of track from a control room.
3) Such a centralized control has been made possible through the provision of
interlocking between switches and signals in the field instead of the levers in
cabin.
4) Movements of all trains is traced on an illuminated diagram in the centralized train
control room known as traffic panel which also shows relative position of signals.
74

75
Interlocking:-
1) The technique achieved through mechanical or electrical agencies for the mutual
locking between the levers of switches and the signals is called Interlocking.
2) An arrangement of signal apparatus that prevents conflicting movements at
junction or crossing or complex yards or sidings.
3) Mechanical connections established between various levers operating the signals
and points in such a way that working of signal mechanism may not go contrary to
the desired purpose.
4) To avoid the possibilities of confusion & danger of pulling wrong signals and thus
to prevent conflicting movements of train which can lead to serious accidents.
5) An interlocking provides for complex train movements and shunting of trains.
6) It provides for the protection of multiple train movements within a localised area.

76
Interlocking:-
 Levers are located at ground level or platform level or in an elevated structure
called signal box or signal cabin.
 The levers are painted for easy identification.
 Devices used: Detectors, Point Lock, Lock Bar, Compensator, etc.
 There are three methods of interlocking
1) Tappets and lock system
2) Key system
3) Route relay system.

77
Railway Track Construction:-
Plate Laying:-
1) The construction of new tracks including carrying of materials to the site and
assembling operation is known as plate laying.
2) Laying out operation on the prepared formation of railway track and connecting up
the rail with sleepers is known as plate laying.
3) Operation of ballast spreading is not included in the plate laying operation.
Rail Head:-
1) The point upto which the new line or track has been laid is known rail head while
the points from where the laying out operation is started is known as base.
2) The progress of the days work is measured in terms of distance from the base to the
rail head.
3) Ballast is not laid in the beginning because in the beginning, formation sets or
settles down and if the ballast has been used in the beginning it will sink in the
formation.

78
Methods adopted for Plate laying are as below:
1) Side or Tram Line Method:
 Useful in flat country or doubling railway track.
 All the material are taken from central depot in material trains to the existing
track and are spread on the formation of new track.
 Assembling is started from one end by manual labor.
2) Telescopic Method:
 Extensively used in India.
3) American Method:

79
Methods adopted for Plate laying are as below:
1) Side or Tram Line Method:
2) Telescopic Method:
 Extensively used in India.
 First of all, large central depot is constructed near the junction of existing railway
and the proposed railway line.
 Plate laying is done totally by manual labor.
 To execute the work, three gangs are formed: Material Gangs, Linking Gangs &
Packing Gangs.
3) American Method: Rails & sleepers jointed together in the central works & then the
complete sets are moved to the site of work to unload & place suitable cranes are
required.

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