Automatic train operation (ATO) is a method of operating trains automatically where the driver is not required or is required for supervision at most. Alternatively, ATO can be defined as a subsystem within the automatic train control, which performs any or all of functions like programmed stopping, speed adjusting, door operation, and similar otherwise assigned to the train operator.
The degree of automation is indicated by the Grade of Automation (GoA), up to GoA4 in which the train is automatically controlled without any staff on board. On most systems for lower grades of automation up to GoA2, there is a driver present to mitigate risks associated with failures or emergencies. Driverless automation is primarily used on automated guideway transit systems where it is easier to ensure the safety due to isolated tracks. Fully automated trains for mainline railways are an area of research. The first driverless experiments in the history of train automation date back to 1920s.
Grades of automation
According to the International Association of Public Transport (UITP) and the international standard IEC 62290-1, there are five Grades of Automation (GoA) of trains. These levels correspond with the automotive SAE J3016 classification: Grade of automation Train operation Description and examples SAE levels GoA0 On-sight No automation 0 GoA1 Manual A train driver controls starting and stopping, operation of doors and handling of emergencies or sudden diversions. Overseen signals due to human errors are safeguarded by train protection systems like ETCS L1. 1 GoA2 Semi-automatic (STO) Starting and stopping are automated using advanced train protection systems like ETCS L2 or 3, but a driver operates the doors, drives the train if needed and handles emergencies. Many ATO systems are GoA2. In this system, trains run automatically from station to station but a driver is in the cab, with responsibility for door closing, obstacle detection on the track in front of the train and handling of emergency situations. As in a GoA3 system, the GoA2 train cannot operate safely without the staff member on board. Examples include the London Underground's Victoria line and New York City Subway's 7 route. 2 GoA3 Driverless (DTO) Starting and stopping are automated, but a train attendant operates the doors and drives the train in case of emergencies. In this system, trains run automatically from station to station but a staff member is always in the train, with responsibility for handling of emergency situations. In a GoA3 system, the train cannot operate safely without the staff member on board. Examples include the Docklands Light Railway. 3 and 4 GoA4 Unattended (UTO) or Manless (MTO) Starting, stopping and operation of doors are all fully automated without any on-train staff. It is recommended that stations have platform screen doors installed. In this system, trains are capable of operating automatically at all times, including door closing, obstacle detection and emergency situations. On-board staff may be provided for other purposes, e.g. customer service, but are not required for safe operation. Controls are often provided to drive the train manually in the event of a computer failure. CBTC is considered a basic enabler technology for GoA4. Examples include the Delhi Metro, Bangalore Metro, Vancouver Skytrain, South Island line and the Thessaloniki Metro.
Additional types Grade of automation Description and examples GoA1+ In addition to GoA1, there is connected on-board train energy optimisation (C-DAS) over ETCS. GoA2+ In case of Amsterdam Metro, a GoA2 is able to reverse in GoA4 at the final stations. This is indicated by '+'. GoA2+ is also present on Bucharest Metro line M5, which uses the same URBALIS 400 CBTC as Amsterdam. GoA2(+) This is GoA2 with additional functions related to metre-gauge railway. GoA2.5 In Japan, this is a form of "driverless operation with an attendant" where the attendant sits in the cab and is responsible for detecting obstacles and making emergency stops in addition to other duties of a GoA3 attendant. Kyushu Railway Company started one of the first revenue demonstration runs of GoA2.5-ready system on the Kashii Line (between Saitozaki and Kashii Stations) on December 24, 2020 while still posting drivers on the train and has since started regular revenue operation without drivers on the entire Kashii Line and beyond. GoA3+ An umbrella term for GoA3 and GoA4 meaning replacement of human train driver. The terms GoA3/4, GoA3,4 and autonomous trains are used synonymously.
Operation of ATO
Many modern systems are linked with automatic train protection (ATP) and, in many cases, automatic train control (ATC) where normal signaling operations such as route setting and train regulation are carried out by the system. The ATC and ATP systems will work together to maintain a train within a defined tolerance of its timetable. The combined system will marginally adjust operating parameters such as the ratio of power to coasting when moving and station dwell time in order to adhere to a defined timetable.
Whereas ATP is the safety system that ensures a safe spacing between trains and provides sufficient warning as to when to stop. ATO is the "non-safety" part of train operation related to station stops and starts, and indicates the stopping position for the train once the ATP has confirmed that the line is clear.
The train approaches the station under clear signals, so it can do a normal run-in. When it reaches the first beacon – originally a looped cable, now usually a fixed transponder – a station brake command is received by the train. The on-board computer calculates the braking curve to enable it to stop at the correct point, and as the train runs in towards the platform, the curve is updated a number of times (which varies from system to system) to ensure accuracy.
When the train has stopped, it verifies that its brakes are applied and checks that it has stopped within the door-enabling loops. These loops verify the position of the train relative to the platform and which side the doors should open. Once all this is complete, the ATO will open the doors. After a set time, predetermined or varied by the control centre as required, the ATO will close the doors and automatically restart the train if the door closed proving circuit is complete. Some systems have platform screen doors as well. ATO will also provide a signal for these to open once it has completed the on-board checking procedure. Although described here as an ATO function, door enabling at stations is often incorporated as part of the ATP equipment because it is regarded as a "vital" system and requires the same safety validation processes as ATP.
Once door operation is completed, ATO will accelerate the train to its cruising speed, allow it to coast to the next station brake command beacon and then brake into the next station, assuming no intervention by the ATP system.
Advantages of GoA3+ In 2021, the Florida Department of Transportation funded a review by scientists from Florida State University, University of Talca and Hong Kong Polytechnic University, which showed the following advantages of autonomous trains: Eliminating human sources of errors Increasing capacity by stronger utilisation of existing rail tracks Reduction of operational costs. Paris Métro reduced its operational costs in case of GoA 4 by 30%. Increasing overall service reliability Improving fleet management and service flexibility Increasing energy efficiency
Accidents and incidents involving ATO While ATO has been proven to drastically reduce the chance of human errors in railway operation, there have been a few notable accidents involving ATO systems: