Safety System Diagram and Requirements

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What is the purpose of the Audio Frequency Track Circuit (AFTC) system?

To transmit MA to the on-board system for ATC

What type of locking is used in Interlocking systems?

Mechanical locking, electrical locking, or electronic locking

What is the primary function of the Despatcher Telephone system?

To provide voice communication between Controllers and agencies involved in safety and/or train operation

What is the purpose of the Leaky Coaxial Cable (LCX)?

To radiate radio waves of a desired frequency along its length Signup and view all the answers

What is the primary function of the Disaster Prevention System?

To collect and display information such as wind, rainfall and rail temperature Signup and view all the answers

What is the purpose of the Interlocking system?

To ensure safety by operating Signals, Points, and other appliances in a proper sequence Signup and view all the answers

What is the function of the Direct Telephone between Adjacent Stations?

To ensure instant and uninterruptible voice communication between two adjacent Stations Signup and view all the answers

What is the purpose of the Despatcher FAX system?

To transmit Fax simultaneously to designated groups Signup and view all the answers

What is the primary focus of safety integrity requirements in a safety-related system?

To determine the likelihood of correct operation of the safety function Signup and view all the answers

What is the purpose of introducing a protection system in a safety-related system?

To trust the system to perform its safety function Signup and view all the answers

Which of the following is NOT a safety function in railway signalling?

Passenger Information System Signup and view all the answers

What is the purpose of SIL in railway signalling?

To give an interval for the rate of safety critical failures Signup and view all the answers

What is the primary concern of safety functions in railway signalling?

To prevent accidents and reduce risk Signup and view all the answers

Which of the following is a safety-related system in railway signalling?

ATP and/or ATC Infrastructure Signup and view all the answers

What is the primary focus of safety system design in railway signalling?

To ensure the correct operation of the safety function Signup and view all the answers

What is the purpose of the temporary speed restriction function?

To change control information indicated for Running Line outside of a Station Signup and view all the answers

Which of the following is a measure of safety integrity in railway signalling?

The likelihood of correct operation of the safety function Signup and view all the answers

Under what conditions shall the Cab Signal sound an alarm?

When the control pattern is received and when the control pattern is updated Signup and view all the answers

What is one of the functions of Interlocking?

All of the above Signup and view all the answers

What does the Centralised Traffic Control System indicate?

The position of a Train on Running Line and Depot Line which has ATC route Signup and view all the answers

What is the function of Train Detection Devices?

To detect a Train on the track for Safety of Train Operation Signup and view all the answers

What is one type of maintenance for the system?

The type is not specified in the document Signup and view all the answers

What is the purpose of the ATC?

To provide automatic train control for Safety of Train Operation Signup and view all the answers

What is part of the functions of Centralised Traffic Control System?

Route clear situation on Running Line and Depot Line which has ATC route Signup and view all the answers

What is the formula for calculating the cumulative time T in the non-repairable case?

T = [t + t + ... + t + (N-k) t] Signup and view all the answers

What is the difference between MTBF and MTTF?

MTBF is for repairable items, while MTTF is for non-repairable items Signup and view all the answers

What is the purpose of a safety function?

To achieve or maintain a safe state of the Equipment Under Control Signup and view all the answers

What is the reliability equation for a constant λ?

R(t) = e^{-λt} Signup and view all the answers

What is an Equipment Under Control Control System (EUCCS)?

A system that responds to input signals from the process and or from an operator Signup and view all the answers

What is the observed failure rate given by?

Gama = k/T Signup and view all the answers

What is the purpose of a safety related system?

To perform one or more safety functions Signup and view all the answers

What is the difference between a safety related system and a safety function?

A safety related system is a system that performs one or more safety functions, while a safety function is a function that is intended to achieve or maintain a safe state of the Equipment Under Control Signup and view all the answers

What is the primary function of the Onboard ATO system?

To control the traction and braking effort to keep the train under the safety threshold Signup and view all the answers

Which component of the CBTC system calculates the limits of movement authority for every train?

Trackside ATS Signup and view all the answers

What is the primary function of the Onboard ATP system?

To ensure continuous control of the train speed according to the safety profile Signup and view all the answers

What is the advantage of CBTC in terms of communication?

Bidirectional communication Signup and view all the answers

What is replaced by CBTC in terms of interlocking?

HW-based interlocking Signup and view all the answers

What is the advantage of CBTC in terms of block principle?

Moving block principle Signup and view all the answers

What is the minimum headway time possible with CBTC?

Less than 90 sec Signup and view all the answers

What is the function of the Data communication system in CBTC?

To facilitate communication between the wayside and onboard systems Signup and view all the answers

What is the primary purpose of the continuous calculation and communication of status by trains in a CBTC system?

To define the points on the line that must never be passed by the other trains on the same track Signup and view all the answers

Which of the following is NOT a CBTC function?

Manual control of train speed Signup and view all the answers

What is the primary difference between a CBTC system and a conventional fixed block system?

CBTC systems use moving blocks, while fixed block systems use fixed blocks Signup and view all the answers

What is the advantage of CBTC systems in terms of communication?

CBTC systems use radio communication, which is more efficient Signup and view all the answers

What is the primary requirement for ensuring passenger safety in metro railway systems?

Ensuring centralized control and monitoring Signup and view all the answers

What is replaced by CBTC systems in terms of interlocking?

Interlocking systems Signup and view all the answers

What is the primary advantage of CBTC systems in terms of block principle?

CBTC systems use moving blocks, which are more reliable Signup and view all the answers

What is the purpose of dividing the railway line into blocks?

To allow multiple trains to use the same line safely Signup and view all the answers

What is the purpose of interlocking in railway signalling?

To prevent derailment by setting points and crossings within safety limits Signup and view all the answers

What is the minimum headway time possible with CBTC systems?

The minimum headway time is dependent on the specific CBTC system implementation Signup and view all the answers

What is the primary advantage of centralized traffic control?

Increasing the line capacity by allowing single-operator control Signup and view all the answers

Which of the following metro systems in India uses a CBTC system from Alstom?

Lucknow Metro Signup and view all the answers

What is the purpose of train detection in railway signalling?

To determine the location of trains for safe operation Signup and view all the answers

What is the primary function of signals in railway signalling?

To provide information to drivers about stopping and speed Signup and view all the answers

What is the primary purpose of block working in railway signalling?

To allow multiple trains to use the same line safely Signup and view all the answers

What is the primary function of automatic block signalling?

To allow multiple trains to use the same line safely Signup and view all the answers

What is the primary function of the Supervisory Control and Data Acquisition System (SCADA)?

To remotely monitor and control traction substations and other related facilities Signup and view all the answers

What is the function of the 'Stick Lock' in the interlocking system?

To lock the turnouts on the set route for a specific time Signup and view all the answers

What is the primary function of the Train Radio System?

For Controllers and Train crew to communicate with each other and exchange data Signup and view all the answers

What is the function of the Transponder in the ATC Device?

To send information to trains for position correction Signup and view all the answers

What is the primary function of the Yard Radio System?

To communicate between station staff and on-board crew during shunting in yard Signup and view all the answers

What is the function of the Track Lock in the interlocking system?

To lock the turnouts when the train is on the track circuit Signup and view all the answers

What is the primary function of the Train Protection Radio?

To alert the train operator to stop and protect a running train in the event of an emergency Signup and view all the answers

What is the primary function of the device which controls signal aspects and turnouts of stations?

To control train operation management from a control centre Signup and view all the answers

What is the primary benefit of the Moving Block system over the Fixed Block system?

Reduced headway between consecutive trains Signup and view all the answers

What is the term used to describe the protected area established by the wayside equipment in a Moving Block system?

Limit of Movement Authority (LMA) Signup and view all the answers

What is the factor that affects the safety margin for location uncertainty in a Moving Block system?

Accuracy of the odometry system in the train Signup and view all the answers

What is the component of a CBTC system that calculates the limits of movement authority for every train?

Wayside equipment Signup and view all the answers

What is the primary benefit of CBTC in terms of block principle?

Dynamic calculation of block boundaries Signup and view all the answers

What is the function of the footprint in a Moving Block system?

To provide a safety margin for location uncertainty Signup and view all the answers

What is the result of the continuous updates of the train location and speed in a CBTC system?

Dynamic adjustment of the safety distance between trains Signup and view all the answers

What is the advantage of CBTC in terms of transport capacity?

Reduced safety distance between consecutive trains Signup and view all the answers

What is the primary function of Trackside ATS in CBTC system?

To manage the traffic according to the specific regulation criteria Signup and view all the answers

What is the advantage of CBTC in terms of block principle?

Moving block principle Signup and view all the answers

What is the function of the Onboard ATO system in CBTC?

To automatically control the traction and braking effort Signup and view all the answers

What is the primary function of the Data communication system in CBTC?

To provide continuous bi-directional communication Signup and view all the answers

What is the minimum headway time possible with CBTC?

Less than 90 sec Signup and view all the answers

What is the advantage of CBTC in terms of interlocking?

Integrated SW based interlocking Signup and view all the answers

What is the primary function of the Onboard ATP system in CBTC?

To ensure continuous control of the train speed according to the safety profile Signup and view all the answers

What is the advantage of CBTC in terms of communication?

Bi-directional communication Signup and view all the answers

Study Notes

Safety System Diagram

A safety system diagram includes the reliability, availability, maintainability, and safety (RAMS) of a system

Safety Integrity Level (SIL)

SIL is a measure of trust in a safety-related system to achieve its required safety function under stated conditions and within a stated period of time
SIL has two purposes:
Gives an interval for the rate of safety-critical failures due to random faults
Defines measures to be applied in design and manufacturing to keep systematic failures low

Safety Functions in Railway Signalling

Important elements of signalling system include:
Interlocking system
Train detection system
Point operation
Signal
ATP and/or ATC infrastructure
Safety functions can be considered safety functions, and SIL is associated with these safety functions, not the equipment

Interlocking

Interlocking means an arrangement of signals, points, and other appliances operated from a panel or lever frame and interconnected by mechanical locking, electrical locking, or electronic locking
Functions of interlocking include:
Track lock
Route lock
Sectional route lock
Approach lock
Stick lock
Signal control

Centralised Traffic Control System

Function of centralized traffic control system includes:
Indication of train position on running line and depot line with ATC route
Route clear situation on running line and depot line with ATC route
Train number of a train on running line and depot line with ATC route

Train Detection Devices

Function of train detection devices:
Detects a train (including vehicle) on the track for safety of train operation

Reliability and Maintainability

Reliability is the probability that a system will perform its intended function for a specified period of time under stated conditions
Maintainability is the probability that a system will be returned to operational status within a specified period of time after a failure
MTBF (Mean Time Between Failures) and MTTF (Mean Time To Failure) are used to measure reliability and maintainability

Functional Safety

Functional safety is part of overall safety that depends on the correct functioning of a safety-related system
A safety-related system performs one or more safety functions

Device Definitions

"Stick Lock" is a lock function of interlocking systems, locking turnouts on a set route for a specific time (release time).
"Track Lock" is a lock function of interlocking systems, locking turnouts when a train (including a vehicle) is on the track circuit.
"Supervisory Control and Data Acquisition System (SCADA)" is a system that remotely monitors and controls traction substations, sectioning posts, and other facilities.
"Train Protection Radio" is a system used to alert the train operator to stop and protect a running train in an emergency.
"Train Radio" or "Train Radio System" is a system for controllers and train crew to communicate and exchange necessary data information.
"Transponder" is a part of an ATC device installed between rails to send information to trains for position correction.
"Yard Radio" or "Yard Radio System" is a system used for communication between station staff and on-board crew during shunting in a yard.

Communication Based Train Control (CBTC) Systems

CBTC is a system that continuously calculates and communicates a train's status via radio to wayside equipment distributed along the line.
The system enables calculation of the area potentially occupied by the train on the track.
It allows wayside equipment to define points on the line that must never be passed by other trains on the same track.

CBTC Functions

Trains continuously calculate and communicate their status to wayside equipment.
The system calculates the area potentially occupied by the train on the track.
Wayside equipment defines points on the line that must never be passed by other trains on the same track.

Moving Block Principle

The moving block principle is a refinement over the fixed block system.
The train position and braking curve are continuously calculated by the trains.
The train communicates its position via radio to wayside equipment.
Wayside equipment establishes protected areas (Limit of Movement Authority) up to the nearest obstacle.

CBTC Architecture

The typical architecture of a modern CBTC system consists of wayside equipment, on-board equipment, and a data communication system.
Wayside equipment includes interlocking, trackside ATC, and trackside ATS.
On-board equipment includes on-board ATP and on-board ATO.
The data communication system includes wired and wireless parts.

Advantages of CBTC

Continuous bi-directional communication based.
Moving block principle vs. traditional fixed block principle.
Integrated software-based interlocking.
No secondary detection needed.
Driverless/unattended operation possible.
Fully automated depots.
Auto coupling possible.
Headway less than 90 seconds.

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