Opening Remarks
Keynote Remarks
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Status of Automated Driving on Subways
by Naoki Sato
Automation is advancing across all sectors of society, from logistics and warehouse operations to familiar areas like automobiles and home appliances. In recent years, developments in generative AI and robotics have brought about systems that operate without human intervention, gradually becoming integrated into our daily lives. Many of you may have already experienced some form of this transformation.
Subways, which support urban mobility, are also taking part in this trend toward automation. In the past, subways were typically operated manually by drivers and conductors, but in recent years, automatic train operation (ATO) systems have been increasingly adopted in countries like Japan and the United States.
In this article, we will explore the definition and classification of automatic train operation in subways, introduce examples of its implementation in Japan, and compare them with the situation in the United States to gain a deeper understanding of subway automation.
When people hear that a train has "automated driving" they often imagine a fully unmanned train with no driver or conductor. However, automatic train operation in the railway industry consists of several levels, which are internationally classified under the “Grade of Automation” (GoA) system.
For example, GoA1 refers to "non-automated operation" (manual operation), where drivers and conductors control acceleration, braking, door operations, and respond to abnormalities. At GoA2, acceleration and braking are automated, while the driver is mainly responsible for monitoring and emergency handling. This GoA2 level is currently widespread in countries such as Japan and the United States, as mentioned earlier. GoA3 is known as "driverless train operation with an onboard attendant" — trains run and stop automatically, with no driver onboard. The attendant, who is not required to be in the front cab, is responsible for tasks such as emergency evacuation guidance. The most advanced level, GoA4, is fully unmanned — all operations, including monitoring, door control, and abnormality handling, are managed entirely by the system.
In Japan, a unique intermediate level called "GoA2.5" — which is not included in the international standards — is also being considered. At this level, a crew member without a train driver’s license rides in the front cab and is responsible for emergency stops, providing a transitional form of operation.
Classification of Grades of Automation (GoA) in railway operation.
(Adapted from Ministry of Land, Infrastructure, Transport and Tourism (MLIT), September 13, 2022, "Railway Autonomous Driving Technology Study Group" p. 2)
In Japan, GoA2-level operation, which eliminates the need for a conductor, is commonly referred to as “one-man operation,” and it has already been implemented on many lines. For example, on Tokyo Metro’s Namboku Line, one-man operation using ATO (GoA2) was introduced when the line first opened in 1991. That same year, the Toei Subway also introduced one-man operation (GoA2) on the newly opened sections of the Ōedo Line. Since then, this system has expanded to other lines, including Tokyo Metro’s Marunouchi and Yūrakuchō Lines, as well as Toei’s Mita Line.
Alongside the introduction of one-man ATO operations, platform doors have also been installed to enhance safety, reflecting efforts to develop the necessary infrastructure for secure automated operations. Through such comprehensive initiatives, urban subways in Japan are steadily progressing toward automation, even if full driverless operation has yet to be realized.
More recently, Tokyo Metro announced that starting in 2025, it will conduct demonstration tests aimed at achieving GoA2.5 operation on the Marunouchi Line, in conjunction with the transition to a CBTC (Communication-Based Train Control) system.
A photo of the platform doors installed on the Namboku Line
（by Metro Cultural Foundation）
Meanwhile, subway automation in the United States began earlier than in Japan. In Washington, D.C., WMATA (Washington Metropolitan Area Transit Authority) introduced GoA2-level automatic train operation (ATO) when the system opened in 1976. However, after a rear-end collision occurred in 2009, automatic operation was suspended. Following various safety improvement measures, ATO was reintroduced on the Red Line in 2024.
While there were plans to expand automated operation to other lines beginning in 2025, issues such as train overruns emerged after the reintroduction. The Washington Metrorail Safety Commission (WMSC) called for thorough investigation and verification before any further expansion. On May 23, 2025, WMATA received approval from the WMSC and began expanding ATO to the Green and Yellow Lines.
In recent years, New York’s MTA has developed plans to upgrade its aging signal systems to CBTC (Communication-Based Train Control), and along with this, the introduction of GoA2-level automatic train operation (ATO) is also being pursued. However, due to the substantial costs involved, it appears that expanding the number of lines with ATO will take many years.
WMATA GoA Initiatives
（Adapted from Washington Metropolitan Area Transit Authority (WMATA), April 24, 2025, “World Class Transit Safety and Operations Committee”, p.9）
Up to this point, we’ve taken a brief look at the state of subway automation in Japan and the United States. But why is automatic operation being introduced in subways in the first place?
One major reason is to address labor shortages. In Japan, where the population is aging and birthrates are declining, it is becoming increasingly difficult to secure sufficient numbers of drivers and conductors. Automation helps reduce the number of required personnel on-site and contributes to maintaining a sustainable operational system. In addition, by systematizing train operations, it reduces human error and improves the precision of on-time performance. (Japan had a high level of punctuality even before autonomous driving was introduced.)
Furthermore, in the case of Japan, automation has been implemented in conjunction with platform doors, helping to create safer environments for visually impaired passengers and others. The advancement of automation in subways is not merely about reducing manpower—it also plays an important role in ensuring safety and peace of mind for a diverse range of users.
To maintain subways—the “lifelines of the city”—in a safe and sustainable way, automatic operation technology will become an increasingly vital tool in the years ahead. While some countries and regions around the world have already introduced GoA4-level fully automated systems, it is our hope that Japan and the United States—each with well-developed existing networks and similar conditions—will deepen their cooperation and continue working toward even better subway systems.
References
Japan Transport and Tourism Research Institute website (Research report on autonomous driving)
Tokyo Metro website:
https://www.tokyometro.jp/news/2023/214836.html (Consideration of GoA2.5 on the Marunouchi Line)
https://www.tokyometro.jp/news/2024/219601.html (Introduction of CBTC on the Marunouchi Line)
Metro Cultural Foundation
Ministry of Land, Infrastructure, Transport and Tourism
WMATA
The Washington Post