Project Overview Union Switch and Signal Inc. (US&S®) provided an Automatic Train Control (ATC) system for service on the LACMTA Metro Green Line Light Rail Transit System in Los Angeles, California.
It is the first light rail transit control system in North America. At one time, the vehicle was capable of being driverless (and it was designed to be driverless). However, this function has been removed to now be Automatic Train Operation (ATO) and Automatic Train Protection (ATP) operation only. Currently, LACMTA is operating the system using train operators. LACMTA directed the car builder not to provide some of the trainlines required to operate in driverless mode; however, the transit control system capability was provided.
The Metro Green Line ATC system controls 19.5 km of a double-track light rail transit line that runs in an east-west direction, from Norwalk west to Aviation Station near the Los Angeles International Airport and then south from the airport through El Segundo to the Manhattan Beach area. The Green Line has a passenger interchange with the Metro’s Blue Line which runs north from Long Beach to downtown Los Angeles.
In service since 1995, the Metro Green Line ATC system features the AF-900™ digital frequency shift-keyed (FSK) track circuit, the MicroCab® on-board cab signaling/vehicle control system, and the MicroLok® vital wayside control system. The heart of the Los Angeles Metro Green Line ATC system is the AF-900 series digital track circuit. Capable of transmitting 76 bits of data to a Green Line train’s MicroCab cab signaling system, the AF-900 track circuit has the capacity to transmit the speed and braking commands necessary for trains to run at closer headways, higher speeds, and in a driverless mode.
In addition to executing vital braking and speed command, the MicroCab system manages a variety of non-vital functions such as speed regulation and station stopping. The MicroLok wayside control system delivers the vital digital vehicle commands to the AF-900 series track circuit through a serial link and executes vital wayside logic required for mainline and depot interlocking control of switches, signals, etc.
The Los Angeles Metro Green Line ATC system is comprised of three subsystems: ATP, ATO, and Automatic Train Supervision (ATS). The ATP system is responsible for vital, safety-critical functions such as train detection, train separation, interlocking control, brake assurance, and speed limit enforcement.
ATO and ATS subsystems address non-vital/non-safety related functions such as programmed stopping, destination control, schedule modifications, speed regulation, door cycling, and train identification.
Also part of the ATS component is a central office-based system, which is responsible for schedule and headway management, control of special train movements, failure detection of wayside or on-board vehicle control equipment, data recording, and the control of trains moving between the storage yard and the mainline.
US&S knows the importance of site modifications and upgrades and continues to provide outstanding service throughout the world. LACMTA is one of many satisfied customers with safer and more effective rail transit systems due to the hard work of Union Switch & Signal Inc.
Key Points • Double track mainline light rail
• Digital FSK track circuits
• Microprocessor controlled interlockings
• Microprocessor controlled on-board cab signaling
Control System • Automatically controlled 15-track storage yard
• Full ATC capabilities including ATP,ATO, ATS
Line Characteristics • Line length: 19.5 km
• Stations: 14
• Operation headway: 2.5 minutes (capability exists for a 60 second headway)
• Station dwell time: 25 – 35 seconds
• Train length: 1 to 3 cars
