Communication-based train control

Definition
Communication-based train control (CBTC) is an automated control system for railways that ensures the safe operation of rail vehicles using data communication between various control entities that make up the system. CBTC is a modern successor of the traditional railway signaling systems which provide a limited control using track circuits, interlockings, and signals.

Overview
CBTC technology is part of the same convergence engineering field as the automotive traffic automation systems. Even though the principles of control between the two transportation domains are quite different, they both are part of the telematics: a CBTC system is based on basic principles from both the automation and telecommunication fields.

A CBTC can provide different levels of railway automation, grouped in the following major functionalities:


 * Automatic Train Protection (ATP)
 * Automatic train operation (ATO)
 * Automatic Train Supervision (ATS)

All CBTC systems operate in the same basic way. An off-board computer can track all trains operating on track linked to the computer. This allows trains to be spaced closer together than on a manually-controlled line. The computer sends information to the computers aboard the train.