Self-Driving Glossary: Terms from ADAS to Zero-Occupant

Advanced driver-assistance systems: features such as adaptive cruise control, lane centering and automatic emergency braking that help a human driver who remains responsible for the drive. SAE Level 1 and Level 2.

Baidu's robotaxi service, operating driverless rides in Wuhan and other Chinese cities and expanding abroad.

A U.S. developer of autonomous trucking technology (the Aurora Driver), running driverless freight in Texas.

The hardware and software that together perform the entire dynamic driving task on a sustained basis, whether or not within a limited operational design domain. The SAE term for Levels 3 to 5.

Tesla's brand name for its standard driver-assistance package (traffic-aware cruise control plus lane centering). A Level 2 system: the driver must supervise at all times.

An approach to perception that relies on cameras and neural networks alone, without lidar or radar. Tesla is its best-known proponent; most robotaxi operators use several sensor types.

The California Public Utilities Commission, which permits paid passenger service by autonomous vehicles in California. The DMV permits the testing and deployment of the vehicles themselves.

General Motors' robotaxi subsidiary, which ran driverless rides in San Francisco until an October 2023 crash and a suspended permit; GM ended the robotaxi business in December 2024.

The two-seat, steering-wheel-free robotaxi Tesla unveiled in October 2024.

A moment when the automated system hands control back to a safety driver, or the driver takes over. California requires permit holders to report disengagements from testing; the figures are hard to compare between companies.

The California Department of Motor Vehicles, which issues the permits to test and deploy autonomous vehicles on public roads in the state, with and without a safety driver.

Everything involved in operating a vehicle in traffic in real time: steering, braking, accelerating, monitoring the road and responding to events. The SAE levels are defined by who performs it and who supervises.

Tesla's paid driver-assistance package, sold as "FSD (Supervised)": a Level 2 system that can navigate city streets but requires the driver to watch and be ready to take over.

The mapped area inside which a robotaxi service operates. Rides begin and end within it; the vehicle will not route outside it.

A high-definition, centimetre-accurate map of lanes, curbs, signals and signs that many robotaxis use as a prior for localisation and planning. Some developers aim to drive without one.

Partial driving automation: the system steers and controls speed together, but the human drives and must supervise continuously. Autopilot, FSD (Supervised), Super Cruise and BlueCruise are Level 2.

Conditional automation: the system drives itself within limits and the human may look away, but must take over when asked. Mercedes-Benz Drive Pilot is the best-known Level 3 system on sale.

High automation: the system drives itself within its operational design domain with no human fallback. Robotaxis such as Waymo's are Level 4.

Light detection and ranging: a sensor that fires laser pulses and times their return to build a 3D point cloud of the surroundings, day or night.

The U.S. National Highway Traffic Safety Administration, the federal regulator that sets vehicle safety standards, investigates defects and, since 2021, requires crash reports from automated-vehicle and driver-assistance operators.

The specific conditions a system is designed to handle: geography, road types, speeds, weather, time of day. A Level 4 system is only automated inside its ODD.

The software stage that turns raw sensor data into a model of the scene: where the road, vehicles, pedestrians and signals are, and what they are.

A Chinese robotaxi and robotruck developer operating in Beijing, Guangzhou, Shenzhen and Shanghai, listed in the U.S. in 2024.

Radio detection and ranging: a sensor that measures the distance and relative speed of objects with radio waves, and works in rain, fog and darkness.

Humans at a control centre who answer a driverless vehicle's questions or suggest a path when it is unsure. Distinct from remote driving: the car keeps control.

A taxi with no human driver on board, hailed from an app and operating within a service area. Waymo, Baidu Apollo Go, Pony.ai and WeRide run commercial services; Zoox and Tesla are entering.

The SAE International standard that defines the six levels of driving automation, from Level 0 (no automation) to Level 5 (full automation everywhere).

A trained employee behind the wheel of a test vehicle, ready to take over. Most services begin with safety drivers before going driverless.

Testing driving software against virtual scenarios, including re-creations of real drives and rare events, at a scale public roads cannot offer.

NHTSA's 2021 order requiring makers and operators of automated driving and Level 2 systems to report crashes involving them, which produced the first national dataset of such incidents.

Alphabet's autonomous-driving company, descended from the Google self-driving car project, and the operator of the largest driverless robotaxi service in the United States.

A Chinese autonomous-driving company running robotaxis, robobuses and robosweepers, with operations in China, the Middle East and Singapore.

A vehicle driving with nobody aboard, for example a robotaxi repositioning to its next pickup. A common phase in a service's permits before paid passengers ride.

Amazon's robotaxi subsidiary, whose purpose-built vehicle has no steering wheel and carries four passengers facing each other.