What is a train control system?

A train control system is the technology that controls the automatic movement of light rail vehicles, such as Muni Metro. Without it, Muni Metro cannot operate.

Train control systems enable communication between trains, traffic signals and other parts of light rail infrastructure. They enforce safe separation between trains based on safe braking distances. They also permit trains to move through subway tunnels faster than allowable when vehicles are operated entirely under human control.

Muni Metro’s Automatic Train Control System (ATCS) – one of the many parts of our light rail infrastructure – has multiple components including computers on-board the trains that are tied into propulsion and brake systems, central and local servers, and communications infrastructure like loop cable signal wires.

This system is currently only installed in the subway. When a train enters the subway, its on-board computer connects to the train control system to run the train in automatic mode, where the trains drive themselves while the operators supervise. When they exit the subway, they disconnect from the ATCS and return to manual operation on the street.

The ATCS is only in the subway currently because the loop cable signal wires are too delicate to install on the street, which is shared with many different types of vehicles that may damage the equipment.