ADVANCED AUTOMATIC TRAIN CONTROL PIONEERED IN SAN FRANCISCO

The development of Bay Area Rapid Transit's Advanced Automatic Train Control (AATC) moving block control system in conjunction with GETS Global Signaling is outlined. The system is based on a robust radio network providing data communication and radio-ranging determination of train location. Computers installed at stations collate location and status messages from trains, calculate train speeds, and control the moving blocks. Each computer is connected to two station radios, which serve as master radios in the network. Spread-spectrum and time division multiplexing are used to communicate with trains every half second. The system was developed to meet the needs of the urban transport industry, rather than for a single customer. Phased installation can reduce disruption. AATC can overlay existing in cab signalling. Station computers are designed to interface to the existing signally for tracking unequipped trains and can also be operated as a stand-alone control system.