Level 4

Cars that drive themselves can do so with varying degrees of skill. Experts therefore distinguish five levels, ranging from simple assistance to a fully self-sufficient vehicle. This classification comes from an international association of automotive engineers, the SAE. Level 4 is the fourth of these stages. A vehicle at this level drives completely on its own within a predefined area: it steers, brakes, accelerates, and monitors its surroundings. If a situation arises that it cannot handle, a human still does not need to step in. Instead, the car brings itself into a safe state on its own, for example by pulling over and stopping at the roadside.

The leap where the driver disappears

The truly decisive difference lies between Level 3 and Level 4. At Level 3, you are allowed to look at your phone while driving. However, you remain the fallback: when the system calls, you must take back control within a few seconds. It is precisely this obligation that disappears at Level 4. As a result, such a vehicle can also drive with no occupants at all, for instance driving empty to the nearest charging station.

Economically, this is the point where business models change. A taxi without a driver no longer has personnel costs, and personnel is the largest cost block in the taxi business. Delivery traffic and buses on fixed routes also become interesting as a result. This is exactly why companies like Alphabet, Amazon, and Chinese providers have been pouring billions into this technology for years.

A common misconception: Level 4 does not mean “drives everywhere.” A Level 4 car can do everything on its own within its area, but outside of it, practically nothing. Only Level 5 would be a vehicle without such limits, driving anywhere in any weather. Level 5 does not yet exist anywhere on the road.

Sensors, maps, and the defined operational area

The vehicle captures its surroundings using several sensor types simultaneously. Cameras provide colors and text, such as traffic lights and signs. Radar measures distances and speeds even in fog. Lidar scans the environment with laser beams and generates a precise 3D image. Software merges these data streams into a single environmental model.

In addition, there is a highly precise map that contains far more than a navigation system. It knows every lane, every curb, and every traffic light position to within a few centimeters. The car constantly compares what it sees with what the map expects. This is exactly why Level 4 only works in places where these maps have been created and maintained in advance.

This area is called the operational design domain. It encompasses not just roads but also conditions: certain districts, speed limits, and sometimes even specific weather. In addition, important components are duplicated, such as brakes and power supply. If one fails, the second takes over, and the vehicle comes to a controlled stop.

Robotaxis in San Francisco, shuttles in German suburbs

The best-known examples are driverless taxis. Waymo, a subsidiary of the Google parent company Alphabet, operates this way in several US cities in regular service. In China, Baidu and Pony.ai offer comparable services. You order a car via an app, get in, and no one sits up front. These vehicles are currently the most visible example of Level 4.

In Germany, Level 4 has been legally permitted since 2021, but only on approved routes. Typical examples are small shuttle buses connecting suburbs or hospital grounds. Such vehicles also operate on company premises, in ports, and in mining, because the environment there remains manageable.

In news coverage, you often encounter the term in connection with stock prices and accidents. The two are related: a single serious incident can cost approvals and billions in market value. So when a manufacturer advertises “autonomous driving,” it’s worth taking a closer look at the level. Assistance systems in ordinary new cars are almost always Level 2, not Level 4.