Driverless Operations Worldwide: Who's GoA 4, Who's Faking It

When transit agencies, vendors, and journalists describe a metro line as “driverless,” they often mean very different things. The term “driverless” is not a technical specification; the technical specification is the Grade of Automation, defined under International Electrotechnical Commission (IEC) standard 62290 with five levels from GoA 0 (line-of-sight) to GoA 4 (Unattended Train Operation, or UTO). At GoA 4 there is no driver in the cab and no operating staff on board. At GoA 3 there is no driver but a member of staff is present on board for passenger assistance, emergency response, or door supervision. A line marketed as driverless can be either, and the difference matters in three places: cost, operating profile, and safety case. As of 2024, by the cleanest available count from UITP’s Observatory of Automated Metros, there are roughly 75 to 80 metro lines worldwide operating at GoA 4 across approximately 45 cities, totaling more than 1,200 route-kilometers. The list of systems that genuinely run at GoA 4, the systems that run at GoA 3 with on-board attendants, and the systems that market themselves as driverless while retaining drivers in selected operating modes is materially different. This post is the practitioner’s guide to which is which.

The GoA framework

IEC 62290 and the closely related UITP framework define five Grades of Automation. GoA 0 is line-of-sight operation with no signaling automation. GoA 1 is fixed-block signaling under driver control with cab-signaling Automatic Train Protection (ATP). GoA 2 is the most common modern Communications-Based Train Control (CBTC) configuration: ATP plus Automatic Train Operation (ATO) under driver supervision, where the driver remains in the cab and is responsible for door operation, departure, and emergency intervention. GoA 3 is Driverless Train Operation (DTO), in which the cab is empty but a member of staff is present on board to supervise doors, assist passengers, and respond to incidents. GoA 4 is Unattended Train Operation (UTO), in which there is no on-board operating staff at all — no driver, no attendant, no on-board staff role at the operational level. The line is run from the central control center, the platform screen doors handle the train-platform interface, and the on-board safety case rests on automated systems plus passenger emergency procedures.

The structural distinction between GoA 3 and GoA 4 is not “is there a driver.” The structural distinction is “is there any operating staff member on board.” GoA 4 systems eliminate this role entirely. GoA 3 systems retain it. The cost, operating profile, and safety case implications are substantial.

Who is genuinely GoA 4

The published GoA 4 reference set, with high confidence, includes the following.

Paris Métro Lines 1 and 14 (RATP, France). Line 14 from October 1998 (greenfield); Line 1 phased 2007–2012 (brownfield conversion). Siemens CBTC. Full-height platform screen doors. Both lines operate UTO. (See Paris Métro Line 14: The Original Driverless Showcase and the Line 1 conversion treatment in Chapter 11 of Communications-Based Train Control (Volume 2).)

Singapore MRT North-East Line, Circle Line, Downtown Line, Thomson-East Coast Line (LTA, Singapore). NEL from June 2003 (Alstom, greenfield); Circle Line from 2009 (Thales SelTrac); Downtown Line from 2013 (Siemens Trainguard MT); Thomson-East Coast Line phased 2020–2024 (Hitachi Rail STS). All four lines operate UTO. Full-height platform screen doors on all stations. (See Singapore MRT NEL: The Original Greenfield CBTC Line.)

Copenhagen Metro M1, M2, M3 Cityringen, M4 (Metroselskabet, Denmark). M1 and M2 from 2002; M3 Cityringen from 2019; M4 from 2020. Hitachi Rail STS CBTC. Full-height platform edge doors. UTO including in maintenance and emergency response phases.

Dubai Metro Red and Green Lines (RTA, Dubai). Red Line from September 2009; Green Line from September 2011; Route 2020 / Expo 2020 extension from 2020. Initial Thales SelTrac, with Hitachi Rail STS for major upgrades and the Expo extension. Alstom Metropolis trains configured for UTO. Full-height platform screen doors.

Vancouver SkyTrain Expo, Millennium, and Canada Lines (TransLink/BCRTC, Canada). Expo Line from 1985 (Bombardier ATC, predating IEEE 1474.1-compliant CBTC); Millennium Line from 2002; Canada Line from 2009. The world’s first large-scale automated rapid transit network. UTO across the system. SkyTrain has now operated continuously for more than 40 years at GoA 4.

Honolulu Skyline (HART, Hawaii, USA). Phase 1 from June 2023. Hitachi Rail STS CBTC. The first US heavy-metro line to operate at GoA 4 from inception. Full-height platform screen doors. (See Honolulu Skyline (HART): The Newest US Metro Built on CBTC.)

Selected Beijing Subway lines including Yanfang (S1) from December 2017, Daxing Airport Express, Lines 11 and 19, plus equivalent lines in Shanghai (Pujiang Line from 2018), Guangzhou, Shenzhen, and other Chinese cities. By 2024, more than 20 Chinese metro lines operated at GoA 4 representing approximately 600-plus route-kilometers.

Several Madrid Metro lines operating with full-height platform screen doors and UTO architecture. Specific line counts vary by source; Metro de Madrid does not always publish GoA grade by line in English-language summaries.

Several airport people-movers including the JFK AirTrain (NYC, USA, 2003), the Denver International Airport Train (1995), the Hartsfield–Jackson Skytrain (Atlanta, USA, 2014), the Dulles AeroTrain (Washington, USA, 2010), and the MIA Mover (Miami, USA, 2020). All operate at GoA 4 on captive airport corridors. (See JFK AirTrain: How CBTC Works on a Driverless Airport System.)

Other European and Asian lines including Nuremberg U-Bahn U2 and U3 (2008 conversion), Barcelona Metro Lines 9 and 10 (selectively GoA 4 since 2009), and Santiago Metro Lines 3 and 6 (2019 and 2022 with full GoA 4).

Approximately 75–80 lines globally operate at full UTO. The rest are GoA 3 or lower, regardless of marketing.

Who is GoA 3, not GoA 4

A second tier of systems operates without a driver in the cab but with a staff member present on board. This is GoA 3, not GoA 4. The distinction is not always made in agency or vendor marketing materials.

The Lille and Toulouse VAL systems in France are classified as GoA 4 in some sources and as GoA 3 with roving attendants in others. Several VAL systems operate as hybrid GoA 4 with on-board attendants, structurally closer to GoA 3 in operational practice.

Several São Paulo Metro lines (Lines 4 and 5) are classified as GoA 4 in some catalogs and as GoA 3 in others. The on-board roving attendant is present in current operating practice. (See CBTC in Latin America: São Paulo, Santiago, and the Quiet Pioneers.) Other Asian and European systems described as driverless similarly retain on-board attendants for passenger assistance.

The structural difference between GoA 3 and GoA 4 affects three things in practice: (1) labor cost per train-kilometer, which is materially lower at GoA 4 because the on-board staff role is eliminated, not just redistributed; (2) on-board safety case requirements, which at GoA 4 must rest on automated systems and passenger emergency procedures rather than on the on-board staff role; (3) regulatory pathway, which at GoA 4 typically requires a more rigorous safety case and certification than at GoA 3. US agencies that adopt GoA 3 with on-board attendants do not capture the labor savings that drive much of the GoA 4 business case in the international literature.

Who is GoA 2 with branding aspirations

A third tier — and this is where “faking it” becomes a useful frame — is metro systems that describe themselves as driverless or as preparing for driverless operation while operating in practice at GoA 2 (driver in the cab, ATP plus ATO under driver supervision). These systems may be technically capable of higher GoA but operate at GoA 2 because of labor agreements, regulatory considerations, or operating preference.

The US heavy-rail metro systems with CBTC — NYCT L Line and 7 Line, BART under TCMP, San Francisco Muni under TCUP — operate at GoA 2. The marketing and the technical capability sometimes describe the architecture as “driverless-ready” or “GoA 4 capable,” but the actual operating mode is GoA 2 with a driver in the cab. This is not a criticism. GoA 2 is the standard US heavy-rail metro CBTC configuration, and it produces real headway, reliability, and energy benefits without the labor-agreement complexity of GoA 4.

The honest read is that the United States operates one full GoA 4 heavy-rail metro line (Honolulu Skyline) plus roughly half a dozen GoA 4 captive airport people-movers. The mainland US heavy-rail metro CBTC fleet operates at GoA 2.

Why the distinction matters

Three things follow from the GoA 3 versus GoA 4 versus GoA 2 distinction that any US transit agency setting a Grade-of-Automation target should price into its planning.

First, the labor cost case for GoA 4 depends on actually achieving GoA 4. UITP comparative studies place GoA 4 labor savings at approximately 40 to 60 percent against equivalent GoA 2 operation. GoA 3 with on-board attendants captures perhaps 20 to 30 percent of that gain because the staff role is redistributed rather than eliminated.

Second, the safety case framework changes materially between GoA 3 and GoA 4. At GoA 4, the on-board staff role does not exist, and the safety case must rest on automated systems plus passenger emergency procedures. Platform screen doors become non-negotiable. The system must be architected for this from the start; GoA 4 retrofits of GoA 3 architectures are non-trivial.

Third, public acceptance follows reliable operation, not marketing. International evidence from Paris Lines 1 and 14, Singapore’s GoA 4 portfolio, Copenhagen, Dubai, and Honolulu shows that public acceptance follows from reliable operation, full-height platform screen doors, transparent emergency procedures, and credible regulatory oversight. None of those agencies marketed the driverless feature as a selling point.

GoA Grade	On-board Staff Role	Platform Screen Doors	Labor Cost per Train-km	Safety Case
GoA 2	Driver in the cab	—	—	Driver supervision
GoA 3	Staff member on board	—	Higher than GoA 4	On-board staff role
GoA 4	No on-board staff	Full-height platform screen doors	Lower than GoA 3	Automated systems

What this means for US transit agencies

Five points follow that any US transit agency setting a GoA target on a CBTC procurement should consider.

First, specify the GoA grade explicitly and align the architecture to it. Do not procure a “driverless-ready” system without specifying which grade is the operational target. Architectural decisions made for GoA 2 do not necessarily extend to GoA 4 without rework.

Second, GoA 4 in the US is achievable on greenfield captive corridors today. Honolulu Skyline is the operational US existence proof. The airport people-mover sector has been GoA 4 for two decades. The structural conditions — captive ridership, full-height platform screen doors, alignment of regulator (FTA, State Safety Oversight) and operator on the safety case — are well-understood.

Third, GoA 4 retrofit on a brownfield US heavy-rail metro is a multi-decade institutional project, not a single procurement. The Paris Line 1 conversion is the realistic precedent: roughly five years of phased cutover after a substantial preparatory period, including labor agreement, platform screen door retrofit, and fleet replacement. The Spanish, Singapore, and Dubai precedents all required equivalent institutional investment.

Fourth, GoA 3 with on-board attendants is a valid intermediate step, but it does not capture the full operating cost case for GoA 4. Agencies adopting GoA 3 should run the operating cost arithmetic against their actual labor framework, not against international GoA 4 reference figures.

Fifth, the US heavy-rail metro CBTC fleet on the mainland operates at GoA 2 today, and that is a defensible engineering choice for the current network. The case for systemic migration to GoA 4 in the US should be evaluated on a corridor-by-corridor basis, with structural preconditions (platform screen door feasibility, labor framework, regulatory pathway) priced explicitly.

Practical takeaways for US transit agencies

• Specify the GoA grade explicitly in the CBTC procurement. Do not use “driverless-ready” as a substitute for a hard target.
• Use the international GoA 4 reference set (Paris Lines 1 and 14, Singapore’s four-line GoA 4 portfolio, Copenhagen, Dubai, Vancouver SkyTrain, Honolulu Skyline) for greenfield US GoA 4 planning.
• Treat GoA 3 with on-board attendants as a distinct product from GoA 4. Run the operating cost case against actual US labor framework, not against international GoA 4 reference figures.
• Do not assume a GoA 2 architecture extends to GoA 4 without architectural rework. Platform screen doors, on-board safety case, and remote passenger assistance are not retrofittable assumptions.
• Anchor public acceptance work on operational reliability, not on marketing the driverless feature. International evidence supports this.

Where to go next

This post is an 11-minute summary. The full treatment of Grades of Automation, including the catalog of operational GoA 4 systems and the comparative safety case framework, lives in Chapter 8 (“Grades of Automation”) and Chapter 11 (“International Benchmarks with US Relevance”) of Communications-Based Train Control (Volume 2). Buy on Amazon. Download Chapter 8 slides (free PDF).

Sources

• Wang, C. (2026). Communications-Based Train Control, Volume 1: Foundations & Technical Architecture. Independent. ISBN 979-8-258-54295-3. — Chapter 8, “Grades of Automation”; Volume 2, Chapter 11, “International Benchmarks with US Relevance.”
• UITP (International Association of Public Transport). Observatory of Automated Metros. uitp.org
• IEC (International Electrotechnical Commission). IEC 62290: Railway Applications — Urban Guided Transport Management and Command/Control Systems. iec.ch
• Régie Autonome des Transports Parisiens (RATP). Lines 1 and 14 Operations. ratp.fr
• Land Transport Authority (LTA), Singapore. MRT GoA 4 Lines. lta.gov.sg
• Metroselskabet Copenhagen. M1/M2/M3/M4 Operations. m.dk
• Roads and Transport Authority (RTA), Dubai. Dubai Metro Operations. rta.ae
• Honolulu Authority for Rapid Transportation (HART). Skyline Operations. honolulutransit.org
• TransLink (Vancouver). SkyTrain Operations. translink.ca
• IEEE Standards Association. IEEE Std 1474.1: Standard for Communications-Based Train Control (CBTC) Performance and Functional Requirements.
• Railway Gazette International. Coverage of Driverless Metro Deployments. railwaygazette.com