Urban population densities are increasing and transit operators are demanding more from their transit infrastructure to reduce headways and increase throughput.
Unfortunately, technology and signalling philosophies developed in the 19th and 20th centuries are not meeting that challenge.
As a result, rail automation is gaining steam. Over the past 30 years, transit operators are shifting to semi or fully automated signalling systems.
The benefits of automation are clear: reduce human error, increase safety, reduce maintenance and increase operational performance but, this comes with a cost in terms of complexity and price tag.
Therefore, how does a transit operator decide how much automation is enough automation for their property?
CENELEC IEC 62290-1:2014 standard focuses on rail automation for public transit systems such as subways, metros or commuter trains referred to as UGT or Urban Guided Transport.
IEC 62290-1 defines the various levels of automation and the minimum mandatory functions required to achieve these levels referred to as Grades of Automation or GoA for short (see table one below taken from IEC 62290-1:2014).
The standard defines five levels of automation:
GoA 0 – Line of Sight Operations
GoA 1 – Non-Automated Train Operation
GoA 2 – Semi Automated Train Operation
GoA 3 – Driverless Train Operation (DTO)
GoA 4 – Unattended Train Operation (UTO)
In order to achieve a GoA level, the system must implement a set of minimum mandatory functions defined for that level.
Table 1: Mandatory functions – “x” denotes it’s the responsibility of operation staff and Sys denotes the “sys” will realize the function
A GoA 0 has no mandatory functions assigned to it and therefore it is considered a dark system or no signalling. All train movements and control of wayside elements (such as switches) are managed by operational procedure.
For example, if a train is required to move from a storage lane to a transfer track, it is the responsibility of the train operator to ensure the switches are in the correct position and ensure the train does not collide with the train ahead.
Procedures govern all aspects of a GoA 0 system. The system does not protect trains.
A GoA 1 system is considered a conventionally signalled system common to all subway or metro systems around the world. IEC 62290-1 has allocated “Ensure Safe Movement of Trains” set of functions.
This means, the GoA 1 system will determine if it is safe for a train to proceed by locking switches and setting the aspect of the signals but, it is the train driver’s responsibility to control braking, propulsion and reading the wayside signals accurately before moving the train forward.
The driver is also responsible for the opening and closing train doors and determining if it is safe to depart a platform.
In a GoA 1 system, the system will determine if it is safe for a train to move forward but the operation staff are the other half of the equation to keep the system safe.
For more details about the mandatory functions that define a GoA 1 system, the following video dives into greater detail.