What do self-driving cars 'think' before changing lanes?

Changing lanes is easy for human drivers. But cars are different. Instead of brains and muscles, self-driving cars make decisions using programming, artificial intelligence (AI), and on-board perception systems like lasers, cameras, and radar.

MagazinePopular Scienceasked four different companies to find the answer: drive.ai (a startup based in Stanford, USA), nuTonomy (from MIT), Uber, and Waymo. The question was: "What are cars 'thinking' when they decide to change lanes?".

Read traffic lights

Signals scattered throughout the environment provide important clues for the robot brain. A drive.ai car can understand that a car stopped at a green light is probably broken down. Algorithms can also conclude that turning on the hazard lights on a car ahead means it won’t go any further.

Deduce

Cars and trucks parked on curves often block part of the road. With self-driving cars, the rule is that a parked car will stay within the lane limits. Smart cars from nuTonomy and drive.ai take that into account when deciding whether to pass. If the car in front is closer to a turn than the center of the road, the robot car may choose to go around it.

Know the way

NyTonomy, which has tested its self-driving cars in Singapore and Boston, has a knack for building up an understanding of urban streets. For example, there are places where a nuTonomy car will be inclined to overtake a parked truck if it comes across one. But if it suspects the car is just stopping temporarily, it will wait behind it—a cautious approach that is quite typical in real life.

Sharing the Streets

The roads are not just filled with cars and trucks, but also with motorcycles, bicycles, and pedestrians. A self-driving car can brake automatically if someone cuts across the road carelessly. Waymo cars can avoid bicycles thanks to a system of cameras, lasers, and radar that recognizes and analyzes all relevant data such as distance and speed to decide what to do.

Changing lanes

Navigation is one of the best reasons for a self-driving car to change lanes. Uber’s team has programmed its cars to check that they have enough distance from other cars before they act. A key factor is the “two-second rule” for calculating safe distances.

Self-contact

A large vehicle can block the view ahead for both human and robot drivers, so a self-driving car following a truck can stay in place until a human intervenes. If the big car in front changes lanes, or flashes its turn signal, the car will try to pass. However, technology now allows vehicles to communicate with each other, and in this way, a parked truck can share its status with nearby cars, like saying, “I’m parked, go ahead.”