Driverless cars won't get rid of crashes

Driver mistakes play a role in virtually all crashes.

So, the logic goes: If you remove people from the equation, far fewer crashes will happen. That’s why automation has been held up as a potential game-changer for safety. But autonomous vehicles might prevent only around a third of all crashes if automated systems drive too much like people, according to a new study from the US Insurance Institute for Highway Safety (IIHS).

According to a national survey of police-reported crashes, driver error is the final failure in the chain of events leading to more than 9 out of 10 crashes. Self-driving cars can account for some human error, but can’t yet account for more complex, prediction-based scenarios, according to the study.

The good news is that self-driving cars excel when drivers are distracted, visibility is low, or a potential hazard is recognised too late. The same goes for crashes due to impairment – caused by drugs and/or alcohol, or a medical emergency. But those types of crashes account for just one-third of all crashes.

To estimate how many crashes might continue to occur, IIHS researchers examined more than 5,000 police-reported crashes from the National Motor Vehicle Crash Causation Survey.

The IIHS team reviewed the case files and separated the driver-related factors that contributed to the crashes into five categories:

• Sensing and perceiving errors included things like driver distraction, impeded visibility and failing to recognize hazards before it was too late.
• Predicting errors occurred when drivers misjudged a gap in traffic, incorrectly estimated how fast another vehicle was going or made an incorrect assumption about what another road user was going to do.
• Planning and deciding errors included driving too fast or too slow for the road conditions, driving aggressively or leaving too little following distance from the vehicle ahead.
• Execution and performance errors included inadequate or incorrect evasive manoeuvres, overcompensation and other mistakes in controlling the vehicle.
• Incapacitation involved impairment due to alcohol or drug use, medical problems or fatigue.

The researchers also determined that some crashes were unavoidable, such as those caused by a vehicle failure like a blowout or broken axle.

“Building self-driving cars that drive as well as people do is a big challenge in itself,” the IIHS said in a media statement, “but they’d actually need to be better than that to deliver on the promises we’ve all heard.”