11.

LINE CAPACITY

11.1 LINE CAPACITY:

The term ‘Line Capacity’, as commonly used on Railways, denotes the maximum
number of Trains that can be run on any given length of the track during a calendar day
of 24 Hrs. The Scott’s Formula is normally used for assessment of Line Capacity of a
given section. According to the Scott Formula:

24 x 60
Line Capacity ‘C’ = ----------------- x η
Trb + To
Where,

Trb: The highest time in minutes taken by the slowest Train to pass over the
Ruling Block section.

To: The average time required for Signalling and Bock operations. On Single
line sections, this would be the interval required between the arrival of the
first Train and the departure of the second crossing Train at the Block
Station at the end of Ruling Block.

η: Efficiency Factor.

11.2 FACTORS INFLUENCING LINE CAPACITY:

From the above Formula of Line Capacity, it should be an easy inference that the
Capacity of the whole section comprising any number of consecutive Blocks is that of
the Block section over which the running Time is largest. This particular Block is known
as the Ruling Block. For increasing the Capacity of section, therefore, it has to be
ensured that such Block sections are kept continuously occupied.

Other major influencing factors as seen from the same Formula are:

(i) Type of Signalling and Control Equipment provided in the

section: Time ‘To’ will depend upon the Standard of Signalling &
Interlocking, type of Block working provided on the section and operating
facilities provided at the Stations.

Examples:

(a) On Single lines, Tokenless Block working will straightaway

yield an advantage of about 10-12 minutes per crossing
over the Token mode of Block working.

(b) Centralised Operation of Points & Signals should result

in saving of a minimum of 3 - 5 minutes of Operations’
Time of Signalling Gears as no exchange of Slots /
 Controls will be involved amongst the different Operating
Agencies.

(c) Block Proving through Axle Counters (BPAC) will result in

saving of 3 - 5 minutes of Operations’ time utilised in
verifying the arrival of Last Vehicle, particularly so for
stopping Trains. BPAC is now an essential component of
Centralised Operation of Points & Signals through PI / RRI.

(d) Automatic Signalling deploys Multiple Aspect Colour Light

Signals, the Aspect of which change automatically by the
Train movement. This cuts out Signal & Block clearance
time and enables closer spacing of Trains, thereby
considerably enhancing the Line Capacity of the section.
Charted Capacity achieved on Automatic Signalling
sections is in the range of 75-130 (Average: 88) Trains
each way while in Absolute Block System, the Charted
Capacity achieved is in the range of 38-58 (Average: 50)
Trains each way. This would mean an average increase of
76% in Capacity with provision of Automatic Signalling.

(ii) Standard of Maintenance of Signalling and Control

Equipment: To ensure that the Capacity is not hampered on account of
failures of Signalling and Telecommunication Equipment, a high degree of
maintenance reliability is required to be necessarily achieved. Chalking
out of an altogether different maintenance strategy of allowing only minor
repairs / modular replacements in the field and doing major repairs /
overhaul in a Central Repair Shop of the Division or Repair / Overhauling
Bench of the Signal Engineer would, perhaps, prove to be a forward step
in this direction.

(iii) Efficiency of the Human Agencies concerned with Train ordering,

Train control, Reception and Dispatch, Running Staff & Maintenance
Staff: Magnitude of the Efficiency Factor ‘η’ also, inter-alia, will depend
upon the type of Signalling and Control Equipment installed in the section.
In the case of sections interlocked to Standard-III and provided with
control circuits, an Efficiency Factor of 70% can usually be assumed. In
CTC Sections, the highest efficiency is achievable because the
Information as to the position of Trains on the entire section is directly
available to the Controller on his Illuminated Panel. He need not ascertain
it from individual SMs. CTC also enables Points and Signals being
directly controlled and in the quickest possible time without the Controller
having to depend upon an Intermediate Agency in the form of the Station
Master. Efficiency Factor for CTC Sections is normally above 80%.

11.3 METHODS TO INCREASE THE LINE CAPACITY OF A

SECTION:

Consideration of the Formula of Line Capacity indicates that the Line Capacity of a
section can be increased by:
(i) Decreasing the running time ‘Trb’ either by increasing the permissible
speed or reducing the length of longer Block sections.

(ii) Decreasing ‘To’ by provision of improved Signalling & Interlocking

arrangement and / or Yard layouts.

(iii) Improving the Efficiency of Operation ‘η’ by providing a more advanced

type of Train Control.

(iv) Maintaining Rolling Stock, Control and Signalling equipment to a high

standard of efficiency.

(v) Ensuring a high standard of Performance in planning the Train

movements - Precedence & Crossings etc.

Other methods to achieve increase in the Capacity could be by adopting one or more of
the following strategies:

(i) Increasing the Capacity by Organisational and Operating Methods:

This will include running of heavier Trains, rearranging Crew and Engine
Links, suitable manipulation of Time Table, elimination of halts for
passenger Trains, elimination of Loading Points for Goods Trains etc.

(ii) Increase in Capacity by Structural Improvements on the Lines like

improved Alignment, reinforcement of Permanent Way, high speed Turn-
outs, elimination of Level Crossings, increase in Capacity of Stations
Sidings, creation of additional Operating Points (viz. Precedence &
Crossing Stations), equalisation of unequal Station-to-Station distance,
partial Doubling on Single line sections etc.

(iii) Improving the performance of Terminal Yards by:

(a) Rationalising the Yard Shunting and Shunting movements.

(b) Framing of Marshalling Orders all over the Railway, as a

whole, with a view to avoiding intermediate handling of
through Trains.

(c) Rationalisation of loading to obtain maximum Block Rake

movements.

(d Providing additional facilities in the Yards, etc.

(iv) By improvement in Telecommunications such as provision of Radio

communications between the Shunting Engines & Yard Staff, between
Control & Station Staff, between Control & Train Crew.

(v) Improved Communication facilities in Control Offices etc.

(vi) Provision of additional Tracks.

Selection of one or more strategies out of those listed in above above, would depend
upon the future development of traffic and priorities for financial investments. Methods of
providing improved Signalling & Interlocking, improved Mode of Working between
Station-to-Station, better Operating facilities at Stations and improving the
Communication facilities will provide higher carrying Capacity on existing Track (s) at
comparatively lower Capital Investments than needed for providing additional lines
(Doubling, Third line and Quadrupling etc.). Keeping in view the scarce financial
resource position prevailing on the Railways and in the Country as a whole, methods
selected in any case has to be one which would generate additional Capacity to match
the increased traffic demands with the least cost to the economy.

11.4 NORMS FOLLOWED ON IR FOR PROVISION OF SIGNALLING

& INTERLOCKING SYSTEMS:

Norms followed on Railways for provision and replacement Works of Signalling schemes
are as under:

Type of the Route Type of the Signalling

Electrified Sections & Multiple Aspect Colour Light

other Important Routes. Signalling

Branch Lines Two Aspect Signalling

Norms followed on Railways with regard to replacement of existing Standard of

Interlocking with higher Standard and provision of suitable Standard of Interlocking in the
beginning of commissioning of a Station / Section are as under:

Maximum permissible Standard of Interlocking

speeds of Trains
through Stations

Un-restricated Std.-III & IV

75 Kmph Std.-II

50 Kmph Std.-I

15 Kmph Rudimentary Interlocking

Norms followed on Indian Railways with regard to provision of System of Working trains
between Block Stations are as under:

Traffic Density (No. of Type of Block Working

Trains / Day)

9-10 Trains Paper Line Clear

 Upto 16 Trains Token Instruments

17-22 Trains Tokenless Block working

22-30 Trains Centralised Traffic Control

More than 30 Trains Patch doubling / Doubling

11.5 SIGNALLING METHODS TO INCREASE THE LINE CAPACITY

ON CONGESTED SINGLE LINE SECTIONS:

A few important improvements on Signalling front, to augment the Line Capacity on

congested Single line sections are enumerated below:

(i) Provision of Centralised Operation of Points and Signals at a

Station.

(ii) Automatic verifications of arrival of Last Vehicle by providing Block

Proving through Axle Counters (BPAC).

(iii) Replacement of Two Aspect Signalling by Multiple Aspect

Signalling.

(iv) Provision of Tokenless working on Single line sections with:

(a) Tokenless Block Instruments.

(b) Continuous Track Circuits.
(c) Digital Axle Counters.

(v) Remodelling the Station Yard Layout to ease out flows and
eliminate cris-cross movements.

(vi) Phased introduction of Automatic Block working with continuous

Track Circuiting or Digital Axle Counters with a provision that as and
when the traffic further picks up, it should be possible to equip the section
with Centralised Traffic Control (CTC) System.

(vii) Provision of Remote Supervisory Train Information System with

Electronic Train Describers, now commonly referred to as Train
Management System (TMS).

(viii) Provision of Centralised Traffic Control (CTC) on long & busy

sections.

(ix) Miscellaneous:

(a) Adoption of a uniform System of Signal Aspects and

indications over a long section to reduce strain on Drivers.
 (b) Improving the Telecommunication facilities, especially on
the Control Communication front in the form of Mobile
Train Radio Communication (MTRC). MTRC shall be an
important aid to running Staff, which apart from equipping
them with instant communication with Control will assure
them that they are not alone in the section. System can
cater for SOS call to draw attention to Station Staff as well
as to other Trains working the section in case any Train
meets with an accident or is held up in the section due to
some emergency.

11.6 TOKENLESS VS TOKEN BLOCK WORKING:

If the additional Capacity requirements on a particular Single line section are not likely to
exceed 15 - 20% for sometimes to come, the Tokenless Block working offers the most
economical method of providing the additional Capacity. Main advantages of Tokenless
working on Token working could be summarised as under:

(i) Increased line Capacity by reduction in crossing time at any Station. The
crossing time taken with Token working varies from 9 minutes to 15
minutes depending upon:

(a) Whether the Station is a 2-line Station or a 3-line Station.

(a) Whether the Main line is along with the Platform or whether
the Main line is a non-Platform line.

(b) The second Train, during a crossing is received on the line

where the SM’s office is situated or on another line to
which access is difficult, when the first Train is standing on
the Reception line nearest to the SM’s Office.

On the other hand, on sections, equipped with Tokenless Block working

either with Block Instruments requiring co-operation of the two SMs at
either end of the section or with non-cooperative type of Instruments, the
crossing time seldom increases from 2 - 3 minutes. A perusal of the two
figures - crossing time with Token working and without Token working
(Tokenless working) would clearly indicate a saving of about 10 minutes
per Train. This can easily account for 10 - 15% increase in the Line
Capacity of the section and also be quantified in monetary terms by
calculating the number of Engine-hours, Wagon-days etc. saved.

(ii) All Trains movements are by Signal Aspects and the Drivers’ attention is
not distracted by exchange of Token.

(iii) There need not be any reduction in Train speed while running through the
Station and there is no necessity at any point of the time for the Driver to
divert his attention from the Route ahead. With Token working, the Driver
has to examine the Token collected by him to make sure that he has
collected only the right Token for the section ahead.
(iv) There is no need of balancing the Tokens, if the number of Train
movements in a particular section is more in one direction than in the
other. With Token working, regular balancing of Tokens is essentially
required, especially so in a section which has frequent uni-directional
traffic. On such sections, the balancing is done every 4th or 5th day. Token
balancing, being the responsibility of Sectional Signal Inspector, he has to
waste his full day for this work thereby resulting in an unproductive work
for about 7-8 days in a month. Granting him 4 - 5 holidays in a month,
practically his half of the salary is, thus, contributed towards balancing of
Tokens. Apart from that, the procedure commonly followed for such
Token balancing is not safe. In fact, for safety of Trains operation during
the process of Token balancing, the Block working should be suspended
which is never done.

(v) Any number of Stations can be switched out without any additional Block
Instruments.

(vi) Increased safety in Train operation through electrical Interlocking

between the Instruments and Signals.

(vii) Tokenless Block working system provides a uniform System of Train

working, as viewed from Driver’s angle for Single and Double line
sections. This type of working is ideally suited for those Single line
sections which are sand-witched between two Double line sections.

(viii) For Token working, a number of ‘Token Pouches’ have to be supplied to

every Station every month as they get damaged due to rough handling. It
has been found that on an average10 Pouches per month per Station are
supplied. In case the Token working is replaced by Tokenless working,
there will be a clear saving towards the cost of these Pouches.

The methods of providing Tokenless block working with the help of continuous Track
circuits or Axle Counters should particularly be preferred on heavy density sections,
where further Signalling inputs in the form of Automatic Block Signalling and / or
Centralized Traffic Control (CTC) shall have to be given in near future for obtaining
additional increase in the Line Capacity. Continuous Track circuiting would be cheaper in
cases where PSC sleepers exist or are being provided on the entire section. Axle
Counters would give an additional advantage in as much as that no Last Vehicle
Clearance checking / verification would be necessary. Count-in and Count-out of Axles
being equal would itself certify that Last Vehicle has arrived and cleared the Fouling
Mark and nothing has been left behind in the section. Provision of Axle Counters as a
means of Block working would also not be infructuous expenditure, even if the section is
to be doubled on a later date as the same equipment and cable can be used for Block
working on Double line.

11.7 SIGNALLING METHODS TO INCREASE THE LINE CAPACITY

ON DOUBLE LINE SECTIONS:

In the following Discussions, it is presumed that the Double Line Section is presently
equipped with Multi Aspect Colour Light Signalling operated Through End Cabin Lever
Frames.
With the above presumptions, the Signalling Methods to increase the Line Capacity on
such a Section are enumerated below:

(i) Remodelling the Station Yard Layout to ease out flows and eliminate
cris-cross movements.

(ii) Automatic verifications of arrival of Last Vehicle by providing Block

Proving through Axle Counters (BPAC).

(iii) Provision of Centralised Operation of Points and Signals at a

Station.

(iv) Phased introduction of Automatic Block working with continuous

Track Circuiting or Digital Axle Counters with a provision that as and
when the traffic further picks up, it should be possible to equip the section
with Centralised Traffic Control (CTC) System.

(v) Provision of Remote Supervisory Train Information System with

Electronic Train Describers, now commonly referred to as Train
Management System (TMS).

(vi) Provision of Centralised Traffic Control (CTC) on long & busy

sections.

(vii) Provision of Flying Crossings (extended loops at a few

intermediate Stations) on congested Single line sections, thereby
enabling two opposite Trains to cross without either of them stopping at
the foot of the Signal or at the Station.

(viii) Miscellaneous:

(a) Provision of Twin Single line working with Axle Counters

on heavy traffic bearing Double line sections, especially
near the Terminals and major Yards to give greater
facilities during accident and to cater for Blocks for various
types of maintenance activities without resorting to
emergency working and its consequential risk.

(b) Improving the Telecommunication facilities, especially on

the Control Communication front in the form of Mobile
Train Radio Communication (MTRC). MTRC shall be an
important aid to running Staff, which apart from equipping
them with instant communication with Control will assure
them that they are not alone in the section. System can
cater for SOS call to draw attention to Station Staff as well
as to other Trains working the section in case any Train
meets with an accident or is held up in the section due to
some emergency.
11.8 REMODELLING OF A STATION YARD LAYOUT:

Remodelling work of a Station Yard Layout with a view to reducing the time required for
a running Train operation would include one or more of the following:

(i) Provision of additional loop lines particularly at Stations closer to

Major Yards / Terminals.

(ii) Provision of adequate Shunting facilities so that no much cris-

crossing movements take place for attaching and detaching of vehicles,
replenishment of Locomotives and watering of Coaches etc.

(iii) Provision of simultaneous Reception & Departure facilities to be

received and departed on / from reception lines at a Station. Figure 11.1
shows typical arrangements for simultaneous Reception and Dispatch
facilities on Double Line sections.

The method listed in sub-para (iii) above, would consequently reduce the delays,
involved in reception of a Train as the Departure Signals for one Train stationed at a
Station & Reception Signal for another Train in the Block section in rear, can be lowered
simultaneously, thereby resulting in saving of time for the Train in Block section to the
extent of 8 to 10 minutes.

11.9 CENTRALISED OPERATION OF POINTS AND SIGNALS AT A

STATION:

A Signalling scheme catering for centralised operation of Signaling gears through Panel
Interlocking / Route Relay Interlocking / Solid State Interlocking, with the provision of
Block Proving through continuous Track circuits or Digital Axle Counters would
significantly reduce the time required for Signalling Operations besides providing
numerous safety features in the System which can, to a fair extent, eliminate the
dependence of human elements in vital checks and verifications.

(i) Centralised operation should obviate the necessity of transferring /

receiving Slots / Controls from different Operating Agencies prevalent in a
Distributed Operating System. Also the Centralised Operation has a ‘Total
View’ of the Operations in his area of Control, in front of him. Decision
making is, therefore, faster and most appropriate to the demanding
situation.

(ii) Last Vehicle Checking is a very important activity on the part of Station
Operating Staff to ascertain that Last Vehicle has arrived complete at the
arrival Station and the Block section in rear is clear. BPAC does it
automatically, saving time and dependence on human element. Location
of Transducers on the Track ensures that Fouling Marks are not infringed.
Figure 11.2 shows schematic of Block Proving through Axle Counters
(BPAC). Block working by Axle Counters, where installed, has resulted in
about 10% to 12% increase in Line Capacity.

11.10 SINGLE LINE WORKING ON DOUBLE LINE SECTIONS:

Intensively used Tracks require periodical Mechanised Maintenance for their proper
upkeep. Blocks (i.e. Single line operation of Double line track) for working Tie-tamping
Machines are not readily available and Civil Engineering Department is experiencing lot
of problems in doing the Maintenance of Permanent Way with Tamping machines. It
may, perhaps, be shocking to reveal that utilisation figure for these costly machines is
not more than 20 - 25%. With more and more Concrete Sleepers coming in on the Main
and Trunk Routes, Track Maintenance with the aid of Machines is now inevitable. In
addition to Mechanised Maintenance of Tracks, Single line working of Double line track
is also required for:

(i) Doing Track Renewal Works with Passer Quick Relaying

System (PQRS) or such other Machines.

(ii) OHE Maintenance and Renewal works.

(iii) Meeting emergent situations, arising out of Accident, Obstruction

on one Track, etc.

The Signalling on a typical Double line Station, as per present practice / policy, is
only directional and thus does not provide facilities either for dispatching a Train on
wrong line (i.e. down Train to up line and vice versa) or receiving a Train from wrong
line at the other end of the section. Given this type of Signalling, switching over to
Single line operation of Double line track would involve:

(i) Backing of the Train through emergency cross over at

dispatching Station.

(ii) Piloting of the Train at the other end of the Station.

If actual observations are taken, it can be seen that available Line Capacity between the
two Stations is reduced to less than the Single line capacity during emergency working.
Though, policy directives exist to cater for bi-directional loops on Double line sections,
such facility will only be helpful in as much as that backing of Train through emergency
cross over would be avoided. Train operations to / from the Block section, however, will
still remain un-signalled. Piloting will continue to be required for dispatch to wrong line
and for reception from wrong line at the other end of the section.

The System details for providing full-fledged Single line working facility on Double line
tracks in event of need / requirement are given in Figure 11.3. In this case, both UP and
DN lines in the Block section can be worked as two Single lines, when necessary.
Normally conventional Double line can remain in operation. Additional Signals would
only be required for dispatching the Train on a wrong line from the dispatching Station
and receiving the same at other end of the section. To cut down the cost, this facility
may be catered for in a limited manner, as shown in the Figure 11.4, to allow reception
from wrong line only on one Berthing Track.

11.11 AUGMENTATION OF CARRYING CAPACITY ON TRUNK &

MAIN LINE ROUTES BY PROVISION OF AUTOMATIC BLOCK
SIGNALLING:
On Indian Railways, Automatic Signalling has been mostly provided on the Suburban
sections only. A few really busy non-Suburban sections on the Trunk & Main line routes
only have been equipped with Automatic Signalling. A major Project of providing Solid
State Interlocking & Automatic Signalling on congested ‘Delhi – Kanpur’ Trunk Corridor
is now under progress.

On Suburban sections, with Track side Signals, Headway of 3 minutes has been
consistently achieved, providing a Line Capacity of around 20 Trains per Hour on each
of the Tracks. On the contrary, Main Line sections typically are carrying 2.5 to 3 Trains
per Hour and Automatic Signalling, so far, has not been favoured on such sections in
comparison with schemes of Doubling / provision of Third Line, presumably for the
reason that these sections carry a mix of the Traffic, where the Train speeds vary from
as low as 40 – 50 Kmph to 120 – 130 Kmph, which poses problems of regulation of slow
moving Traffic to give precedence to the high speed Trains. In reality, the picture should
be otherwise as Automatic Signalling can certainly provide significant increase in Line
Capacity on these sections with minimal inputs.

Rules and Operating Procedures for Train Running in Absolute Block System Mode of
working are quite Complex, Cumbersome and Time consuming. No doubt the Rules in
vogue are really comprehensive and have been employed to ensure that the Operating
Staff deployed at Stations for Train Running Duties do not make mistakes. Accidents do
occur when the Procedures are compromised and violated.

At a typical Way side Station, equipped with Centralised Panel Interlocking System for
Operation of Signalling Gears, the Station Master performs the following functions before
a Train can be Signalled to be Received and Passed through his Station:

(i) Granting Line Clear to Station in Rear and be in readiness at his

Station to receive the Train. Record the Information of Granting /
Receiving Line Clear in Train Signal Register (TSR).

(ii) Inform Telephonically, under the exchange of Private Numbers, to all

the Manned LC Gates under his Control (Both in Station Section and in
the mid Section) to Close and Lock the Gates against Road Traffic for the
Incoming Train. Procedure of exchanging the Private Number itself is
quite tedious. He has to repeat the Number twice in a definite manner, cut
the Number from his Private Number Book and record the same in Train
Signal Register (for each Transaction). On an average, there could be 2-3
LC Gates under the control of Station Master per Section.

(iii) Set the Route for the Incoming Train. Thanks to Centralised Panel
Interlocking System, the time consumed in this activity is minimal.
Imagine if the Station is equipped with End Cabin Signalling. Slot Control
shall additionally be required in that situation.

(iv) When the Train arrives at the Station, Station Master has to exchange
All Right Signal with the Train Guard to ensure the Complete Arrival of the
Train, before the Line can be Closed and Block Instruments for the
Section can be Normalized. Again the Entries regarding Train Entering
the Section, Train Received Complete at the Station, Closing of the Line
etc. etc. are to be recorded in TSR. If the Section is provided with BPAC,
 this activity of Exchanging All Right Signals with the Guard is not
required.

(v) For Departing the Train the Line clear has to be obtained from the
Station in advance, and the Route is to be Set & Locked, duly recording
the Information in TSR.

(vi) Section Controller is to be kept informed of the timings of Arrival and

Departure of each Train.

Above is rather a simplistic view of the Procedure as the Station Master, in addition, is
also required to interface with Maintenance Staff for various Maintenance Activities as
also for Granting of Block etc., do the assigned Commercial Duties of the Station and
answer to the Public regarding their Train Running Information Queries.

On Double Line Sections, the activities listed above get doubled.

Imagine a Double Line Section carrying 60 Trains each way (120 in both Directions) in
24 Hours and the quantum of activities performed by the Station Master. He has to
repeat all the Transactions on an average every 12 minutes.

Rigorously following of the above Train Running Procedure, beyond a certain limit of
Train Traffic Materialisation, does cause some real avoidable Bottlenecks in smooth
running of Traffic and often Operating Staff are found not observing the laid down Rules
and Procedures in the spirit in which these have been framed. Slight abnormal situation
may aggravate the situation to the hilt and Staff may violate the Rules and Regulations
and thus compromise with Safety.

Outcome of this Mode of working is Clear. We are running around 2.5-3 Trains per Hour
in each Direction against the possibility of some 15-20 Trains. If the Automatic Block
Signalling is provided on the Section, the whole Process gets quite simplified.
Transactions for Block Working, Transactions with LC Gates (as all LC Gates shall be
Interlocked and provided with Audio Visual Approach Warning and Approach Locking
Mechanism) and also the Exchanging of all Right Signals with the Guard (as the Section
is completely Track circuited) are totally eliminated. Station Master also becomes
reasonably Stress free and can act to counteract abnormal situations as and when these
are encountered.

To further drive the Point Home, in a better manner, of the real potential of Automatic
Signalling, following Table provides a comparison of Line Capacity obtainable on some
two adjacent Sections equipped with Automatic Block working and Absolute Block
working:

SN Automatic Signalling Adjacent Section equipped % Increase

Section with Absolute Block
Working
Section Charted Section Charted
Capacity Capacity
1. Sini- 130 Rajkharswan- 47 176%
RajKharswan Jharsuguda
(SER) (SER)
 2. Sini-Tata 102 Tata- 49 108%
(SER) Kharagpur
(SER)
3. Palwal- 70 Mathura- 47 49%
Mathura Agra (CR)
(CR)
4. Vatva- 70 Anand- 45 55%
Anand Vadodara
(WR) (WR)
5. Ambala- 75 Ambal- 53 41%
Rajpura Panipat
(NR) (NR)
6. Rajpura- 75 Sirhind- 54 39%
Sirhind Ludhiana
(NR) (NR)

Traffic Potential Achievable with Automatic Signalling

Data given in the above Table amply illustrates the Postulation that Automatic Block
Signalling on Trunk and Main Line Routes also can provide significant increase in
achievable Line Capacity.

11.12 RULING BLOCK:

The term ‘Ruling Block’ is used for the Block section over which the running Time is
largest. For increasing the Capacity of the section, therefore, it has to be ensured that
such Ruling Block sections are kept continuously occupied.

Ruling Block influence the Line Capacity in a big way. This can be easily inferred from
the Formula of Line Capacity:

24 x 60
Line Capacity ‘C’ = ----------------- x η
Trb + To
Where,

Trb: The highest time in minutes taken by the slowest Train to pass over the
ruling block section.

To: The average time required for Signalling and Bock operations. On Single
line sections, this would be the interval required between the arrival of the
first Train and the departure of the second crossing Train at the Block
Station at the end of Ruling Block.

η: Efficiency Factor.

Longer the length of Ruling Block, smaller will be the achievable Line Capacity on that
section. Line Capacity can be, thus, effectively increased by decreasing the running time
‘Trb’ over the ‘Ruling Block’ either by increasing the permissible speed or reducing the
length of longer Block sections.
11.13 PROVISION OF TWIN SINGLE LINE WORKING ON DOUBLE
LINE SECTIONS:

Line Capacity of a section is also greatly affected by the Signalling facilities provided at
Terminals and major Yards. Perhaps, there won’t be any significant advantage in
increasing the throughput of the section, if matching facilities in Yards and Terminals are
not provided. In order to pump out the traffic efficiently from Yards and Terminals,
provision of Twin Single Line Working, at least for two or three Block sections, on either
side should be an economical solution. This type of working also called ‘Reversal
Working’ has an added advantage in that if there is bunching of Trains in the same
direction during any part of day, Trains can be moved much more expeditiously by
passing them over both the tracks. Moreover, if one of the lines is not available due to
maintenance or accident or some other reason, the dislocation to the traffic would be
relatively much less.

Twin Single Line Working can either be provided by the use of Single Line Tokenless
Instruments or with continuous Track circuits or with Electronic Axle Counters. Solutions
with continuous Track circuits or Axle Counters should be preferred as in this case there
won’t be any need for Last Vehicle Clearance checking / verification.

11.14 CENTRALISED TRAFFIC CONTROL:

Since CTC includes Centralised Control, Panel Interlockings at wayside Stations,

elimination of necessity to verify the Complete Arrival of Trains and Tokenless working,
the potentialities of CTC in increasing the Line Capacity are significant. Main benefits of
providing CTC are:

(i) Increase in Line Capacity: The provision of Centralised Traffic

Control on congested Single line system increases their Line Capacity to
the extent of about 40% - 50%. Increase in Capacity is due to the
following features:

(a) Reduced Crossing Time: Time taken for picking

up of Token, bringing it upto the Block Operating location,
extracting a new Token and handing over the same to the
Driver accounts for a total time of 10 to 15 minutes. With
CTC, it is possible to take off the Signals for the first Train
while the second Train is still moving and has not
completely stopped at the Station. Not only this, driver of
the first Train remains aware of the time as to when the
Signal for his Train shall be taken ‘OFF’ after arrival of a
Train from opposite direction and, therefore, he starts
practically within half a minute or even earlier after the
Signal has been cleared for his departure.

(b) Quick Starting of the Goods Trains: Normally

when a Goods Train is brought to a stop, the Driver does
not know when he is likely to be allowed to proceed ahead,
particularly when it happens to be a time for passenger
Trains. He, therefore, takes it easy and does not worry
 about and when the Signal is taken ‘OFF’, either he is not
in his Cab at all or he is not ready to start due to one
reason or other. This accounts for further delay in
departure of the Train. In case of CTC, Driver has to be
always alert as he knows that his Train will be kept on
moving and may be stopped for overtaking or crossing
purposes for a few minutes only. Further if he delays
starting of his Train, he knows that it is going to be
detected and got recorded on Automatic Train Graph
Recorder. He is, thus, always conscious that in case of
failure on his part in not starting the Train in time, he is
likely to be questioned. Fear of this detection and
questioning ensures that the Driver will start his Train as
soon as the Signal is taken ‘OFF’.

(c) Overtaking of Trains: Provision of Automatic

Block Signalling enables the overtaking operation to be
over within a minimum possible period. While a Goods
Train or a slow passenger Train is approaching a Station,
there may be a faster Train in rear and as soon as the slow
Train is berthed on one of the lines at the Station, the
faster Train is given precedence. Again after the faster
Train has cleared the next Signal, the Goods Train / slow
Passenger Train can start immediately behind it. Thus
detention to slow moving traffic i.e. the Goods Trains are
reduced considerably. This, in turn, results in better
average speed of Goods Trains and Shunting van trains.

(d) Proper Planning of Train Movement: CTC

system places complete information and execution of
various functions in the hand of Operator on the Central
Console. This means that there is no delay in ascertaining
the location of Trains in the section or in acting to change
Routes to take care of unexpected conditions since it is
unnecessary either to call and question a remote Station
Master or to transmit instructions nor is there any
hindrance in expeditious handling of the situations
because of changed conditions. In addition, elimination of
intermediate Operators viz. the Cabinmen and Station
Masters etc., removes the opportunity for division of
responsibilities.

(ii) Increased Safety in Train Operation: Because of the complete Track

circuiting of the Block section as well as Station Yards, the safety of Train
operation is increased, as it is no more possible to clear any Signal for an
occupied line. The visibility of Colour Light Signals is also better which
further aids the Driver in better control of his Train.

(iii) Economy in the Expenditure of Staff: With the provision of CTC, it is

possible to eliminate most of the Operating Staff from the wayside
 Stations. Staff will only be required at wayside Stations for the following
purposes:

(a) Commercial work.

(b) Keeping a watch on the Axle of moving Trains (for

detecting of Hot Boxes etc.).

(c) Controlling the Shunting Operation.

While the modular design of the System, wherein the Maintenance Staff
will only be required to detect the particular Module at fault and then
replace it with the new one / already repaired one in a Central Repair
Shop, the strength of S&T Maintenance Staff also can be significantly
reduced.

(iii) Increased facilities in Maintenance of Permanent Way: Track

Maintenance, when we are going in for mechanised tamping through
Track Tie Tamping Machines is simplified with CTC. CTC Operators can
see at a glance on the Control Console what Train situation exists at any
given location. It is, thus, possible for the CTC Operator to set up Signals
and Route so that Maintenance Staff can move or work without delay and
take advantage of the maximum gap available between Trains.

CTC can be introduced at roughly 1/3 rd of the cost of Doubling of saturated Single line
sections. Whenever there is an increase in the number of Trains beyond a saturation
point on a Single line or Double line, the solution generally sought is the provision of
additional track i.e. Doubling of Single line or providing a 3 rd line in case of Double line
and so on. Provision of additional track means heavy initial Capital cost and increased
recurring expenditure. Provision of CTC on such congested sections at about 1/3rd of the
cost of Doubling, would result in the Sectional capacity being increased to the extent of
40 - 50%, postponing the need of additional track for many years to come and at the
same time yielding rich dividends on the Capital investment. CTC Installations in many
parts of the World have shown that this mode of Signalling makes it possible to affect
notable increase in the Line Capacity, while all other factors such as track alignment,
gradient and form of the motive power have remained unchanged.

CTC along with Remote Supervisory Train Management System can provide complete
control of 200 to 300 Kms. of a section from a Central location and also monitor the
actual running of Trains therein to take corrective action as and when required. With
rapid pace of computerisation, powerful systems are now available to optimise the
sectional Line Capacity. It can provide for proper precedence to slow moving Trains with
faster Trains suffering only a minimum detention. Automatic Block Signalling, being an
essential ingredient of CTC, the Block operating time is completely eliminated. The
system can generate Line Capacity to much more than 100 Trains each way from the
present Capacity of 50 to 60 Trains.

CTC can be introduced in following phases:

(i) Provision of Tokenless Block working by using

continuous Track circuits or Electronic Axle Counters.
(ii) Provision of Panel Interlockings at wayside Stations on
the section in question.

(iii) Provision of Automatic Block Working on the section.

(iv) Provision of Remote Supervisory Train Management

System with Train Describers.

(v) Provision of equipment for conducting the operations at

various wayside Stations from the Central Control Centre Office.

11.15 FLYING CROSSINGS AND PRECEDENCES:

With the introduction of CTC on Single lines, the Line capacity can be increased to the
extent of 40 – 50%. If a further increase in the Capacity is required, it could be done by
providing Flying Crossings, thereby enabling two opposite Trains to cross without either
of them stopping either at the foot of the Signal or at the Station. This is a concept, which
can be used prior to undertaking partial or full Doubling of the section. It is, however,
necessary to foresee with certainty as to at which Station (s), the extended loops for
providing such crossings would produce the best results. The lengths of loops required
for Flying Crossings will depend upon the length and speed of the Trains.

On Double line sections, extended loops can be provided at select Stations to cater for
Flying Precedences on the lines similar to Flying Crossings. A sample study done by
Western Railway on ‘Surat-Vadodara’ section, has brought out that in comparison to the
Third line Project on the same section, the proposal of extended loops with Automatic
Signalling, CTC and Remote Supervisory Train Management System would cost 31%
less and meet the requirements. Concept of Flying Precedence is shown in Figure 11.5.

11.16 REMOTE SUPERVISORY TRAIN MANAGEMENT SYSTEM

(TMS):

Present System of Manual Exchange of Train Movement Information from / to Stations

and to / from Control Office, though provides some Assistance to the Train Controller in
taking timely and optimum Decision for Train controlling in case of any unusual event
that puts Operations out of gear, it is not of much help when Traffic density on the
Section increases to a reasonably high level. In such a case, the Controller merely gets
reduced to a Plotter to plot the Train Movements on the Chart and accord his advice
here and there with regard to allowing Precedence and for Regulating the Traffic through
the Section. Situation is worse on Suburban Sections, where the Trains run in the
Section at a Head way of 3 minutes or so.

Similarly, Information in Real Time is not available to the ASMs for ensuring correct
Displays and Announcements. To match the high Volume of Traffic and that on
Suburban Sections in particular, it is essential to provide ‘On Line’ Information of Train
Movements to the various Operating Agencies viz. the Controller and ASMs, who can
then take timely and effective Steps in case of Disruption of the Operation. This is
achieved by a Supervisory Train Management System (TMS).
The Discussion on TMS, hereafter, shall be in relation to the Suburban sections but is
equally applicable to Trunk & Main Line sections carrying Heavy Density Traffic and
particularly to those equipped with Automatic Signalling Schemes.

TMS can be visualized as an ‘On Line’ System for regulating Trains by monitoring their
Movements and taking timely Decisions for Diversion of Trains, Induction / Withdrawal of
Rakes, Planning of Reversal of Rakes etc. TMS shall also provide timely Information to
the Commuters through Display Boards and Announcing System.

11.16.1 Brief Functions of TMS:

(i) ‘On Line’ Display of Movements of all Trains on Video Monitors

(VDUs) as well as over Indication Panel, located in the Control Room.

(ii) Automatic Recording and Retrieval of Train Movements.

(iii) Interfacing with the Train Indicator Boards at various Stations.

(iv) Provision of Video Display Units (VDUs) for Train Running

Information to the Commuters.

(v) Interfacing with the Announcements System for facilitating Auto

Announcements.

(vi) To Provide for Remote Control Operation of Signalling &

Interlocking System, at a future Date, if so needed. This would mean that
TMS can be upgraded to facilitate Remote Operation of Signalling Gears
as well, in addition to the Remote Supervision. The facility can be planned
in a Selective manner also.

(vii) Generation of MIS Reports and Statistical Data.

Refer to Figures 11.7 & 11.8 for Photographs of a Working Train Management System
(TMS) on Suburban sections of Western Railway.

11.16.2 Benefits from TMS System:

(i) Assistance to the Controller:

(a) Availability of ‘On Line’ Display of Movement of all Trains,

including their Identification. This gives complete picture to
the Section Controller about Train Running on the entire
Section and thus helps him to take timely and proper
Decisions for cancellation, Diversion and Termination
including Induction / Withdrawal of Rakes in case of any
Disruption to the Train Services due to any unusual
Occurrences.

(b) Provides the current Status of all Interlocking Information

pertaining to various Stations i.e. Signals, Points, Track
 circuits etc. Thus failure of the same and consequential
hold-up of the Trains are suitably taken care of.

(c) System with the use of Audio / Visual Alarms calls for the
Attention of the Controller for timely action, when a Train is
held up for the longer duration at a particular location /
Signal (say, for more than 5 minutes).

(d) Overview position of availability of various Rakes on the

Sidings, Car Sheds etc. helps in taking optimum Decision
regarding Retrieval / Induction of Rakes from / into the
System.

(e) Real Time Graph assists in prediction about further

Movement of particular Train up to the Destination.

(ii) Assistance to Station Managers:

(a) ‘On Line’ Displays on the VDU Screen gives the expected Arrival
Time of next 2 Trains from each line. This enables him in optimum
Planning of Train Movements in his jurisdiction.

(b) Cases of Diversion from Slow to Fast Corridors or vice-versa /

Cancellation of Trains, are automatically flashed on his Screen,
well in advance enabling him to ensure correct Operation of Train
Indicator Boards and timely announcements about Cancellation /
Change of Platform.

(ii) Assistance to Commuters:

(a) VDU Screens provided at the Entrance of each Station as

also on the Foot-over Bridges & Platforms shall indicate
Scheduled Arrival as per Time Table and Expected Arrival
of next 2 Trains from each line.

(b) Indicator Boards at Stations shall be directly operated from

the System, on ‘On Line’ basis. Thus possibility of wrong
Displays due to manual Operation are avoided.

(c) With the availability of ‘On Line’ information about the Train
Movements, the timely Announcements shall be possible,
as Information of Expected Arrivals of various Trains
including Cancellation / Diversion is automatically available
to ASM / Indicator Operator / Announcer, well in advance.

(iv) Management Information System (MIS) Capability:

Following analysis / Reporting shall be possible:

(a) Punctuality Analysis in a suitable Format on Daily, Weekly

or Monthly basis.
 (b) Analytical Report of various unusual occurrences like
Signal failures, OHE Break Downs, Rake failures etc., on
Daily, Weekly or Monthly basis.

(c) Analytical Report of Crew Link / Utilization.

(d) Analytical Report of Rake Link Utilization.

(e) Simulation Studies on the effect of various Parameters on

Sectional Density like Addition / Deletion of a signal etc.

11.16.3 General System Details:

TMS is a Computer based System located in the Control Office, which collects Signalling
Status Information (Status of Signals, Points, Track circuits etc.) from the various Station
Interlockings in Real Time basis. It also collects Train Identification Information (Train
No., Rake No., Name of Crew and Platform No.) from the Train Originating Station,
where it is manually fed (Note: In an Advanced System, the Train / Rake Information
can be made to be picked up from the Track side Devices in the Driving Car through an
Antenna mounted beneath the Car Frame).

The above Information is processed automatically and Display regarding various Train
Movements together with Status of Signals, Points, Track circuits etc. become available
on the Controller’s video Screen on Selective Station / Section basis. Display Information
is also made available on a big Wall Indication Panel located in front of the Controllers,
covering the entire Section.

System primarily comprises of:

(i) Control Office Equipments comprising of Master Controller / Server,

Operators Terminals and Wall type Display Panel.

(ii) Way side Station Equipments including Terminals at enquiry and

Announcement System.

(iii) Communication Network linking Way side Stations with Control Office.
Nework, typically, shall be of Distributed Multi-drop type on 64 Kbps data
Channels on Optical Fibre Link.

(iv) Public Display and Automatic Announcement System, comprising of

Display Boards, VDUs and Speakers located at Strategic locations.

Master Controller / Server:

Main Functions of Master Controller / Server shall be:

(i) To Access Data from all Way side Stations Interlockings through
common Communication Link and display Status of Trains and Signalling
Information.
(ii) To accept Data from the Controller and from other Movement
Agencies i.e. ASMs of Train Originating Stations.

(iii) To furnish necessary Information to Display Panel for the display

of Train Movements with Identification, Track circuits, Points & Signals
and Alarms etc.

(iv) Communicate with the Maintenance Terminal and Terminals

provided with various Controllers.

(v) Provide MIS Information for Report Generation and other

Functions.

Master Controller shall be connected with all Station Interlockings through a suitable
Interface. Information / Status of Track circuits, Signals, Points, Route Set etc. shall be
transmitted from Way side Stations to Master Controller.

Controller Terminals:

Controllers shall have multiple Wide Screen High Resolution Graphic Colour Video
Terminals with dedicated Key Boards, Mouse and / or Tracker Ball. From these
Terminals. Controller can map any area on the Section for displaying Signalling
Information as well as Train Description Information.

Controller shall have the facility to enter the Train Description in to the System. Usually,
this Information shall be fed by the Originating Station.

Selection on controller terminals shall be Menu based.

It shall also be possible to have simultaneous display of different Images of Information

on the video through multiple Windows.

Wall type Display Board:

This Display shall provide controllers an Overview of the complete System in terms of
Train Running Information and Track layout, Status of Points, Aspect of Signals, Level
crossing Gates etc. Indication Panel shall in addition display the occupancy of various
Track sections along with the Train Description.

Way Station Terminals:

All the Stations shall be provided with VDU Terminals. ASMs at the Train Originating
Station will be able to enter the Train Identification and its Location (Platform Line No.).
This Information shall then be automatically communicated to Master Controller on the
Communication Link. In case, the Number is not keyed-in, same can be shown as
Flashing at the Location of the Train. Controller also having this keying-in facility can
then enter the Number and as soon as the Train Number is keyed-in by the Controller,
flashing shall stop.

Station Manager can have display of Track layout together with the Trains Identity for the
Area under his control, which shall be automatic and continuous.
Block Schematic of Supervisory Train Management System (TMS) is shown in Figure
11.6

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