Automatic train operation (ATO) is an operational safety enhancement device used to help automate operations of trains. This is achieved according to the Grade of Automation (GoA) present, up to GoA 4 level, where the train is automatically controlled without the presence of staff on board. ATO is primarily used on automated guideway transits and rapid transit systems which are easier to ensure safety of humans. Most systems elect to maintain a driver (train operator) to mitigate risks associated with failures or emergencies.
Many modern systems are linked with Automatic Train Control (ATC) and in many cases Automatic Train Protection (ATP) where normal signaller operations such as route setting and train regulation are carried out by the system. The ATO and ATC/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 coast when moving and station dwell time, in order to maintain the timetable defined for it.
Types of train automation
- GoA 0 is on-sight train operation, similar to a tram running in street traffic.
- GoA 1 is manual train operation where a train driver controls starting and stopping, operation of doors and handling of emergencies or sudden diversions.
- GoA 2 is semi-automatic train operation (STO) where starting and stopping is automated, but a driver operates the doors, drives the train if needed and handles emergencies. Many ATO systems are GoA 2.
- GoA 3 is driverless train operation (DTO) where starting and stopping are automated but a train attendant operates the doors and drives the train in case of emergencies.
- GoA 4 is unattended train operation (UTO) where starting and stopping, operation of doors and handling of emergencies are fully automated without any on-train staff.
Operation of ATO
Whereas the ATP is the safety system which ensures a safe spacing between trains and provide 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 (it 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 then 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. 
Urban passenger railways
- On the London Underground, the Victoria, Central, Northern, and Jubilee lines run with ATO. The Victoria line, opened in 1968, was the world's first full scale automatic railway and also the first to have an ATO system replaced. The Circle, District, Hammersmith & City and Metropolitan lines are currently being modernised with a brand new automatic train control system.
- The Glasgow Subway has been using ATO since 1980.
- The PATCO Speedline between Philadelphia, Pennsylvania and Lindenwold, New Jersey, opened its first segment in 1969 as the first ATO line in the United States. (The Expo Express, which ran during the World's Fair Expo 67 in Montreal, was the first in Canada and in North America.)
- The Montreal Metro Green, Orange and Blue lines have been using ATO since 1977.
- On the MTR Network in Hong Kong, all lines operated by MTR Corporation have run with ATO since 1979. The former KCR East Rail Line network has used ATO since 2002.
- Many trains in Japan use some level of ATO. A notable example is the Yurikamome line in Tokyo, which is GoA 4.
- Bay Area Rapid Transit (BART), opened in 1972, was the first new metro system with multiple lines built with ATO.
- The Vancouver SkyTrain in Vancouver, British Columbia, is an automated and driverless system commissioned in 1985.
- On the Mass Rapid Transit (Singapore), all lines operating currently run with ATO since 1987.
- All of the lines on the Docklands Light Railway in London have been using ATO (GoA 3) since it opened in 1987.
- On the Nuremberg U-Bahn, existing U2 and new U3 lines were converted to ATO in 2008, with one-year mix service.
- On the Barcelona Metro, the L9 (Europe's longest driverless line), L10 and L11 run with ATO.
- The Tren Urbano, which serves the San Juan metropolitan area, has a Siemens ATC system that allows for fully automatic operation.
- On the Milan Metro, the M1 Red Line and the M3 Yellow Line run with ATO.
- São Paulo Metrô, Line 4, opened 2010, is the first system operating GoA 4 in South America.
- On the New York City Subway, the BMT Canarsie Line (L train) began full ATO operation using CBTC in June 2012. IRT Flushing Line (7 and <7> trains) similarly underwent track and signal modernization, with full ATO operation beginning in November 2018.
- On the Thameslink railway in the core section between St. Pancras and Blackfriars
- The trains on Dubai Metro don't have a driver, neither do the trains on AnsaldoBreda Driverless Metro and on Line C of the Rome Metro
- The trains on Doha Metro recently started operation, running automatically in ATO without a driver 
- Aerotrain (KLIA) in Kuala Lumpur, Malaysia uses a GoA 4 ATO system.
- On the Los Angeles Metro system, the Red Line, Purple Line, and Green Line use the GoA 2 ATO system.
- Indonesia's capital city, Jakarta, recently introduced public transport (Jakarta MRT) that uses the ATO with GoA 2 Level.
- New South Wales's capital city Sydney in Australia, has the Sydney Metro which opened in 2019 and operates with GoA Level 4. Sydney is also in the process of upgrading older lines in the network to eventually enable GoA 2 and higher in the future.
- The Washington Metro is possibly the first system in the world to revert back to (mostly) manual operation from ATO, following a crash in 2009. However, GoA 2 is still installed on all lines and is planned to be used again in the future.
- The Prague Metro historically operated GoA 1 system ARS on all lines. GoA 2 is available on line C (PA 135 by Siemens) and line A (LZA by AŽD Praha). As of 2020, line B is transitioning from ARS to LZA. The projected line D should operate unattended.
- The Rio Tinto Group "AutoHaul" system on its iron ore railways in the Pilbara. This system is GoA 4 capable, able to run trains without a single person aboard for the entire trip out to the mines and back to the port. In October 2017 the first fully autonomous test took place over a 100 kilometres (62 mi) section. The group was granted accreditation by Australia’s Office of the National Rail Safety Regulator, approving the autonomous operation of iron ore trains in the Pilbara region of Western Australia.
- The Czech railways utilize GoA2 operation since 1991. Currently, about 400 vehicles are equpped with on-board units. 1500 km of lines (of total 9000 km network) are equipped with lineside part of ATO, next 1500 km are covered by data for GPS localisation.
High speed rails
- CR400BF-C 'Fuxing Hao', a variant of CR400 Fuxing series, running on Beijing–Zhangjiakou intercity railway is the world first high-speed rail service capable of driverless automation in commercial operations. The specific Grades of Automation (GoA) was not announced.
Many railways are planning on using ATO. ATO was introduced on the London Underground's Northern line in 2013 and will be introduced on the Circle, District, Hammersmith & City, and Metropolitan lines by 2022. Although ATO will be used on Crossrail and Thameslink, it has not yet been implemented on UK mainline railways. The U-Bahn in Vienna gets an ATO in 2023 on the new U5 line. All lines being built for the new Sydney Metro will feature driverless operation without any attended staff present. The Toronto Subway and RT is undergoing signal upgrades in order to switch to have the system running on ATO over the next decade. ATO (AVV system) is in everyday operation on Czech Railways lines since 1991, since 2008 also in test operation with ETCS. The Delhi Metro officials have stated that driverless trains with advanced features will run on the Botanical Garden - Kalkaji corridor with trial runs planned for the last week of July 2016 and the trains being operated on the route from August 2016 onwards. Initially, drivers will be deputed to operate the trains but they will be gradually withdrawn said a metro official. In recent times UK railway had operated train with ATO over ETCS Level 2 using Grade of Automation 2 where the train control and protection was provided by ETCS rather than ATP or ATC.
- List of automated urban metro subway systems
- Automation of the London Underground
- Communications-based train control – A moving block signalling system that can be used to automate operation of trains
- One-man operation – A method of train operation, sometimes seen as an intermediate step towards greater automation
- Personal Rapid Transit
- Autonomous car
- Guided bus
- International Association of Public Transport. "A global bid for automation: UITP Observatory of Automated Metros confirms sustained growth rates for the coming years" (PDF). Belgium.
- Elisabeth Fischer (23 August 2011). "Justifying automation". Railway-Technology.com.
- "ATO". Railway Technical Web Page. Archived from the original on 12 April 2012.
- "Driverless operations start in Nürnberg". Railway Gazette International. Archived from the original on 2009-07-01.
- www.railway-technology.com Tren Urbano Rapid Transit System, Puerto Rico - Accessed 2011-07-12
- "Linea M1, nuovo sistema di regolazione della circolazione ATM, Azienda Trasporti Milanesi". www.atm.it.
- New York City Transit - History and Chronology Archived October 19, 2002, at the Wayback Machine.
- "MTA L Train Response to Squadron" (PDF) (Press release). Metropolitan Transportation Authority. 2011-09-06. Retrieved 2011-10-29.
- "New York Flushing Line CBTC contract awarded". Railway Gazette. 2010-06-28. Retrieved 2011-10-29.
- Ward, Victoria (2018-03-26). "First self-drive train launched on mainline track". The Telegraph. ISSN 0307-1235. Retrieved 2018-03-29.
- "Rome's subway: the eternal project". 17 April 2016 – via Japan Times Online.
- https://www.railway-technology.com/features/doha-metro-project/. Missing or empty
- "Rio Tinto has confirmed that it is on track to completely transition to driverless trains across its entire Pilbara operation by the end of 2018". iseekplant.com.au. July 20, 2017. Retrieved 1 September 2017.
- "Rio Tinto operates first fully-autonomous test train". Railway Gazette. October 2, 2017. Retrieved 5 October 2017.
- Ltd, DVV Media International. "Rio Tinto's automated trains approved". Railway Gazette. Retrieved 2018-05-23.
- "China's Fuxing series, can run up to 350 kilometers per hour (217 mph) without a driver". CNN. 8 January 2020.
- "World's fastest driverless bullet train launches in China". The Guardian. 9 Jan 2020.
- Wheeler, Charles (2008-12-17). "Yonge Subway Extension – Recommended Concept/Project Issues" (PDF). TTC.
- Rajput, Abhinav (April 28, 2016). "South Delhi-Noida direct Metro connectivity by August". HT Media Limited. Hindustan Times. Retrieved 10 May 2016.
- "Thameslink first with ATO over ETCS". Railway Gazette. 20 March 2018.