Deploying CBTC - Key functions to understand

As the world of Metros have started showing interest in Communications-based train control (CBTC) signalling system , when deploying CBTC , operational critical functions are important features, which define how railways operate. If these functions are neglected then the operator can expect service service disruptions and may take long to recover.

Mainly Functions Defining CBTC split into two Major categories:

 1)   Core Functions

2)   Non-Core Functions

Core Functions

•  Automatic Train Protection (ATP) : Continually checks that the speed of a train is compatible with the permitted speed allowed by signalling , maintaining the safe distance between trains
• Automatic Train Operation (ATO):Controls timetable , dwelling time , starting /stopping positions ..etc
• Automatic Train Supervision (ATS):The subsystem within automatic train control that monitors trains, adjusts the performance of individual trains to maintain schedules, and provides data for adjusting service to minimize the inconveniences otherwise caused by irregularities.

 *Core functions are mostly fixed in scope and non-core functions can be influenced by the operators.However, Operators have influence over the design of non-core functions because the Operator’s personnel and the riding public interact directly with these functions

 Of the numerous non-core CBTC functions, following are key functions

non-core CBTC functions

• Train recovery : In a signalling system with no secondary train detection(track circuits or axle counters), this is a critical function when a train is unable to communicate with the wayside. there are various recover options available.
• Work zone protection : Creating a safe corridor for workers at track level while maintaining Service level. This functions take greater importance because trains are either driverless or operating in an automated mode.
• Engineering trains with CBTC equipment : This a decision not a function but a decision to include engineering trains under CBTC or not and operationally, a critical one.
• Diagnostics : Effective diagnostics allow a CBTC system to localize and pinpoint problems, permitting the Operator to quickly recover from Service affecting faults. There are three levels of diagnosis architecture available
• Fallback mode : Fallback mode is a mechanism to track trains using secondary detection devices such as track circuits or axle counters. The cost of implementing a fall back mode will outweigh the marginal benefit this function provides.
• Launching trains : CBTC signaling must treat the depot and mainline as a single entity, otherwise the boundary becomes a barrier for launching trains into service.
• Cutover strategy : Right cutover strategy tob transition from conventional signalling to CBTC with minimum impact to Service