CBTC Overview Flashcards
Primary aim of CBTC
Provide fail safe rail signalling operating, preventing hazards such as collisions between trains. It also allows trains to travel at the maximum speed consistent with safety.
Safe separation distance
A dynamically calculate distance between trains based on operating speeds, braking curves and locations of the trains on the guideway.
Safety distance
A fixed distance between the commanded stopping point of the following train and the confirmed position of the rear of the preceding train.
Vehicle Control Centre
The VCC transmits the target point for trains to stop and calculates the safe separation distance for the following train.
Automatic Train Protection
ATP is responsible for safe train movement:
- Provides point interlocking
- Provides safe train separation
- Prevents hazards such as unscheduled door openings, roll back ect
- Maintains continuous train location determination throughout the system.
Automatic Train Operation
ATO is responsible for speed regulation, station stopping and door control:
- Regulation of train speed within the limits imposed by ATP
- Provide programmed station stop including door opening
- Provide alarm monitoring and reporting
Automatic Train Supervision
ATS provides a HMI via the system management centre:
- Provides system admin capabilities
- Provides a line overview
- Routing trains
- Regulated the operation of trains to maintain timetables
- Displays KPIs
VCC Overview
VCC provides ATP and commands vehicle operation and route setting. It is responsible for safe train separation and safe movement of points. 14 VCCs on the 4LM network.
VCC Components
3 CPUs working in a 2-out-of-3 configuration
VCC Data Communication System
Input/output racks
Station Controller Subsystem
SCS communicates with the VCC and other SCSs. It is responsible for the safety of the system within its area of control. Receives inputs from:
- Emergency stop devices
- Point status
- Axle counters
- Protection key switch
- Peripheral equipment
VOBC Overview
The VOBC provides ATP and ATO. It is responsible for train movement within the speed/distance permission from the VCC. Each S Stock has two VOBCs fitted for redundancy.
VOBC Communications
The TIU mounted on the underframe reads information from the track mounted transponders. The VOBC uses this information to determine its position on the guideway. The VOBC via the DCU transmits this information to the wayside equipment.
Transponders
The maximum distance between transponders is 75m. There must be 3 transponders every 100m. Four types of transponder:
- Crossover transponder
- Cross border transponder
- Border transponder
- Accurate stop transponder
Crossover transponder
Basic transponder used by the positioning system. They replace crossovers found in a loop based system and are used to maintain positioning.
Cross border transponder
Contain information to assist in establishing and maintaining positioning around virtual loop boundaries. They are placed on either side of a border transponder.
Border transponder
These replace loop crossovers/boundaries in a loop based system and are used to maintain and establish positioning. They also replace EFID loops at transition zones so positioning can be established when entering the system from non-CBTC territory.