People in San Francisco have discovered a ridiculous way to both “prank” self-driving cars and protest their existence by doing a process called “coning”. The simple trick involves placing a single traffic cone on the bonnet of the vehicle, which appears to fully disable the car and makes it immediately stop, switch its hazard lights on, and wait for recovery. 

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It is unclear exactly why the cars do this, but it likely comes down to a safety mechanism that identifies objects in front or on top of the car's bonnet and stops it, preventing further injury. This would prevent hit-and-runs of pedestrians, for example. 

The trend started with activist group Safe Street Rebel, who took issue with recent incidents involving autonomous vehicles. A vehicle from General Motors’ Cruise subsidiary collided with a bus recently, while another autonomous car hit a dog, which Safe Street Rebel claim is part of the reason for their rebellion against increasing self-driving prevalence. 

Instead of self-driving vehicles, the group hopes that policy will incentivize public transport, improve pedestrian access, and reduce reliance on cars. 

Soon, California will decide whether regulations stopping autonomous vehicles from driving at certain times will be lifted, allowing them to operate at all hours. The group have condemned this bill and are now seeking for people to cone autonomous cars in protest.  

Local news outlet KRON4 said that city officials believe this protest could cause disruption and congestion as self-driving cars are stopped in their tracks. 

Autonomous vehicle operator General Motors said to TechSpot that, despite incidents, their vehicles have never caused any fatalities or serious injuries, while a spokesperson for another operator, Waymo, described the protests as "vandalism".