Page 106 - 捷運技術 第35期

98 Alstom Company New Enhancement of the Taipei Metro Signaling System

Throughout the history of the Taipei metro system, Alstom Signaling has been the signaling
company of choice to provide signaling systems for DORTS. All of the Taipei Metro lines, with the
exception of the Muzha line, are signaled by Alstom systems. Alstom Signaling continues to
provide safe and reliable ATC signaling systems for the Taipei Metro with new and improved
features added to the Orange and Blue line extension（OBLEX）project. For those unfamiliar with
the basics of a metro signaling system, we shall first provide a brief summary.

A modern mass transit ATC signaling system is comprised of three fundamental sub-systems:
ATP, ATO, and ATS. Theses sub-systems work together to ensure safe and efficient train operation.

Automatic Train Control System

The ATP system is primarily responsible for ensuring safe separation between the trains. The
entire length of the main train track is divided up into sections called Blocks. The basic premise is
that no two trains should occupy the same block at the same time in order to avoid a collision.
Additionally, faster moving trains need greater separation from the trains ahead due to increased
stopping distance required. The ATP system is informed of which blocks are occupied by means of
track circuits. Each block of track is supplied with an electrical signal, at a specific frequency, that
runs through the rails and through the bonds（a large transformer at each end of the track circuit）.
When a train occupies the track circuit, the signal is interrupted and a track relay（in the signal
equipment room）will be de-energized. The de-energized contacts of the track relay are used to
inform the ATP system that the block is occupied.

Speed commands to the trains are also supplied to the trains by means of signals injected into
the rails through the bonds. When the ATP sub-system senses that a track circuit is occupied, it will
automatically adjust the speed commands for trains approaching that section of track. By this
method, the ATP system can ensure safe separation of trains while allowing the maximum speed for
efficient train operations.

The second part of the ATC signaling system is the Automatic Train Operation sub-system.
When the train receives a permissive speed command（a speed command above 0 Kph）, the ATO
computers aboard the train command it to smoothly accelerate to the maximum allowable speed.
As the train approaches the next station, it passes over wayside markers which electronically inform
the ATO system what distance remains to the next station. The ATO computers then begin to
smoothly decelerate the train so that it will stop precisely at the station. When the train is stopped
correctly at the station, the ATO system will be able to communicate with the station’s berthing
system. This communication allows the train doors to open properly. When the station dwell time
expires, the doors will close and the train accelerates to make its run to the next station. All these
functions are controlled by the ATO system.

The ATS system allows Central Control Room（CCR）personnel to monitor and control metro