What Do L1/2/3/4 Mean? A Comprehensive Guide to Autonomous Driving Levels

With the rapid development of intelligent technology over the past two years, "autonomous driving" has become widely discussed. This technology not only frees our hands and feet, greatly enhancing travel convenience, but also significantly improves driving safety. After all, technology is far more accurate than human subjective operation in terms of precision and judgment. Dangerous driving behaviors and road rage incidents, which have led to numerous accidents, will likely become a thing of the past. Many are eagerly awaiting this future.

Today, we’ll clarify the different levels of autonomous driving so that you won’t be confused when hearing about "L2/3" and other technological driving features promoted by car manufacturers.

Currently, the classification of automotive intelligence is primarily determined by two authoritative industry organizations under the U.S. Department of Transportation: the NHSTA and SAE International. The levels are divided into five categories: L1, L2, L3, L4, and L5.

L1 Level - Assisted Driving

Assisted driving features are found on most mass-produced vehicles today. Examples include lane change assistance (which uses warning lights on the exterior mirrors to alert the driver to approaching vehicles), lane departure warning (which alerts the driver with steering wheel vibrations or audible warnings if the vehicle drifts out of its lane), automatic parking (which helps the driver park by automatically identifying nearby parking spaces), and cruise control (which maintains a set speed without the driver needing to control the throttle). The key characteristic of L1 features is that they do not include active driving technology. In essence, vehicles with L1-level autonomous driving still rely on the driver for control, offering assistance and warnings as needed.

L2 Level - Semi-Automatic Driving

L2 level, also known as semi-automatic driving, includes features such as lane keeping (which automatically corrects the vehicle’s direction if it drifts out of its lane), adaptive cruise control (ACC) (which automatically adjusts speed and maintains a safe distance from the vehicle ahead, even braking if necessary), and active braking (AEB), which triggers an alarm and may apply the brakes automatically if the system detects an imminent collision. Some models, like those from AITO, are classified as L2+, and certain advanced models, such as Tesla or Xpeng G3, may feature high-level steering functions that assist with lane changes without manual intervention, sometimes referred to as L2.5.

L3 Level - Highly Automated Driving

Vehicles with L3-level technology can independently perform nearly all driving tasks, without requiring the driver’s intervention.

L4 Level - Ultra-High Automated Driving

L4 level, also known as ultra-high automated driving, allows remote control of the vehicle and true fully autonomous driving. A driver can issue commands to the vehicle, which will understand and execute them safely without human intervention. This requires advanced systems and high-throughput 5G data transmission. At this stage, driving schools might become obsolete.

L5 Level - Fully Automated Driving

L5 vehicles are fully autonomous, transforming into a movable living space. You can relax, sleep, or engage in other activities while the vehicle handles all driving tasks, using comprehensive analysis of road conditions, weather, and other factors to choose the safest and most efficient route.