Basic GoA2 automation is the ability to control propulsion and braking based on the conditions of the track ahead. Achieving this level of automation is a significant accomplishment but it is not enough for a modern urban transit system.
The next step is to increase the level of trackside/platform awareness and control, which brings us to the next Grade of Automation, GoA 3.
A GoA3 system is aware of its surroundings along the track.
Trackside devices installed along the track detect obstacles that may obstruct train movement such as tunnel ventilation doors or work crews performing maintenance at track level. These devices connect to a wayside unit that sets the movement authority for all trains.
Another approach is for the train to “look” ahead and determine if there are any obstructions along the track. On-board devices such as LIDAR map the track ahead and identify potential hazards or obstructions in front, which the train uses to determine if it will slow down or stop altogether.
At the platform, a GoA 3 system must monitor for unauthorized opening of platform doors and/or the activation of platform emergency stop devices and create a protection zone if either occurs.
The majority of CBTC based systems around the world are GoA3 because this is a level of automation most operators expect; control over the train, aware of trackside hazards and control over the platform.
The following video provides more details of the functions that define a GoA 3 based system.
GoA3 Explained - Driverless Train Operations