Ask Hackaday: Why do driverless cars continue to cause traffic jams?

Despite what some people may tell you, self-driving cars are not yet on the market. Instead, there are a small handful of startups and large tech companies that are rapidly developing prototypes of this technology. These vehicles are being tested furiously in various cities around the world.

In fact, depending on where you live, you may have spotted them outside. Not least because many of them continue to cause traffic jams, much to the dismay of their fellow road users. Let’s dive in and see what’s wrong.

Elevation zero: San Francisco

Waymo operates a fleet of fully self-driving vehicles in cities including Phoenix and San Francisco. Credit: Waymo

Two of the biggest companies in the autonomous car space are Cruise and Waymo, affiliated with General Motors and Alphabet, Google’s parent company, respectively. Both operate prototype fleets in San Francisco, with the city offering a perfect base for autonomous vehicle training. The bustling metropolis is not without problems, with many narrow streets, heavy traffic and various types of public transport to contend with.

So it’s no coincidence that San Francisco has become ground zero for stories of self-driving car disasters. In December, a cruise vehicle stopped at a red light and later refused to move for thirteen minutes. In January, a Waymo car blocked an intersection during rush hour, much to the anger of other road users. Others blocked buses and groups of cars got lost in the thick fog.

Emergency crews have also come into conflict with the vehicles. In distressing scenes, a driverless cruise vehicle tried to drive through an area where firefighters were battling the blaze in the city centre. The vehicle nearly ran over fire hoses, stopping only after a firefighter smashed the car’s windshield. This is not an isolated incident either. In a more recent incident, public safety officials resorted to lighting torches and yelling before eventually getting an autonomous vehicle to stop at an emergency scene. Meanwhile, a Waymo vehicle was caught near a parade, eventually responding to hand signals from a police officer to get out of the way.

Error: Path not found

In some of these cases, the cause of the problems is obvious. For example, in heavy fog, a driverless car will obviously lose visibility of the road around it and may decide that driving further is too dangerous. Another possibility is that rain, dirt or snow can cover the sensor, completely blinding the vehicle. However, unlike a human, it may not have the skills needed to safely find a place to stop. To avoid injury, cars may simply stop where they are, unfortunately blocking roads in the process.

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