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Advances in Communications-Based Train Control Systems by F. Richard Yu

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1
Chapter 1
Introduction to
Communications-Based
Train Control
Li Zhu, F. Richard Yu, and Fei Wang
1.1 Introduction
Rapid population explosion has resulted in a series of problems, such as trac jam,
environment pollution, and energy crisis. Recently, there has been a strong desire
around the world to improve the rail transit speed and capacity in order to relieve
the pressures from already-busy roads to address the need for fast, punctual, and
environmentally friendly mass transit systems.
e train signaling systems need to evolve and adapt to safely meet this increase
in demand and trac capacity [1]. e main objective of communications-based
train control (CBTC) signaling system is to increase the capacity by safely reducing
Contents
1.1 Introduction .................................................................................................1
1.2 Evolution of Train Signaling/Train Control Systems ....................................2
1.3 Main Features and Architecture of CBTC Systems ......................................5
1.4 Challenges of CBTC Systems .......................................................................7
1.5 Projects of CBTC Systems ............................................................................8
1.6 Conclusion .................................................................................................13
References ...........................................................................................................13
2 Advances in Communications-Based Train Control Systems
the time interval (headway) between trains traveling along the line. Specically,
CBTC makes use of the communications between the railway track equipment
and the train for train control and trac management. Because the exact position
of a train is known more accurately than with the traditional signaling system, the
railway trac can be managed more eciently and safely.
As dened in the IEEE 1474 standard [2], a CBTC system is a “continuous,
automatic train control system utilizing high-resolution train location determina-
tion, independent of track circuits; continuous, high-capacity, bidirectional train-
to-wayside data communications; and trainborne and wayside processors capable
of implementing automatic train protection (ATP) functions, as well as optional
automatic train operation (ATO) and automatic train supervision (ATS) functions.
In this chapter, we rst present the background and evolution of train signaling/
train control systems. en, we introduce CBTC systems, followed by the main
CBTC projects around the world.
1.2 Evolution of Train Signaling/Train Control Systems
e main objective of a train signaling/train control system is to prevent collisions
when trains travel on the railway track. erefore, a common ingredient of various
types of train signaling systems is as follows: the locations of the trains must be
known by the system at some level of granularity.
e rst generation of train control architecture includes track circuits for train
detection, wayside signals to provide movement authority indications to train oper-
ators, and trip stops to enforce a train stop [1]. Figure1.1 illustrates this architec-
ture. In Figure1.1, if track circuit TC5 is occupied (shunted by a train), the signal
at the entrance to TC5 displays a red aspect. If block TC3 is unoccupied and TC5
is occupied, the entrance signal to TC3 displays a yellow aspect. If both TC1 and
TC3 are unoccupied, the entrance signal to TC1 displays a green aspect. ese
signals are separated by the trains safe braking distance (SBD), which is calculated
and set at a sucient length for a train to stop safely from the maximum operating
speed specied for the track section. We can see that, in this system, a green aspect
means that two blocks (or at least twice SBD) are clear ahead of the signal; a yellow
aspect means that one block (at least SBD) is clear ahead of the signal; and a red
aspect means that the block ahead has a train occupying the track circuit.
TC1TC3 TC5
Figure1.1 Train signaling system using wayside signals.

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