The HCS Project
will upgrade our current signalling system to a new one. This new system will use
Communications Based Train Control (CBTC) technology.
Perth's current signalling system
Perth’s urban rail network currently uses a fixed block signalling system. The track is divided into segments, known as ‘blocks’, with a three aspect (red, yellow, and green) colour-light signal at the start of each block. The Automatic Train Protection (ATP) system translates the signal aspect into a speed at which the train is allowed to travel and enforces this speed limit through the train’s braking system.
For our railcar drivers, the aspect lets them know what’s occurring on the track ahead and whether it’s safe to proceed.
- A red signal means stop, the next block is unsafe to enter. ATP will apply brakes to stop the train if it tries to pass the signal.
- A yellow signal tells the railcar driver that the next block is safe to enter, but the following signal will be red, and they must prepare to stop. ATP will determine where braking is required and apply the brakes when needed.
- A green signal indicates that this block and the next block are safe to enter, and the railcar driver can travel through at the maximum allowable speed.
This existing ATP system has been in operation since the early 1990s, is approaching its end-of-life and needs to be replaced.
How a Communications Based Train Control system works
With a CBTC
system, the train’s location is determined based on beacons installed on the
track, which are read via an antenna fitted to the undercarriage of the train.
Combined with the measurement of wheel rotations, this verifies the location of
the train as it travels between beacons. Devices onboard the train continuously
transmit real-time information on the precise location, speed, and operational
status of all fitted trains back to PTA’s Public Transport Operations Control
Centre.
This real-time information allows the CBTC system to create a protective bubble, or a moving block, that moves with the trains along the line. Only one train is allowed in this block at any time.
With a moving block signalling system, the size of each train’s protective bubble is adjusted in real time by calculating the train’s braking distance. It considers factors including the train’s current speed, the gradient of the track ahead, and brake performance. If at any time the network loses contact with a train, automatic safety controls will stop the train until contact is re-established.
This provides the capability to safely reduce the space between trains, while removing signalling as a constraint to increasing train services in the future.
