What Sort of Accidents Can We Expect From Self-Driving Cars?

According to researchers Michael Sivak and Brandon Schoettle at the University of Michigan Transportation Research Institute, an analysis of the 2013 on-road safety record of self-driving vehicles reveals four main findings:

• Current best estimates for self-driving cars indicates that the autonomous vehicles have a higher crash rate per million miles traveled than do conventional vehicles.
• Because the 95% confidence levels in the data overlap, it is possible “that the actual rates for self-driving vehicles are lower” than those for conventional vehicles.
• Self-driving vehicles were not at fault in any crashes they were involved in.
• The overall severity of injuries in the crashes involving self-driving vehicles has been lower than the severity of injuries in conventional vehicles.

The authors note two important caveats. First, 50 self-driving cars had accumulated just 1.2 million miles of on-road travel, compared with 269 million vehicles that logged more than 3 trillion miles for the conventional vehicles. Second, the self-driving cars are driven only in limited and less demanding conditions than conventional cars.

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Self-driving cars were involved in 11 crashes between 2012 and 2015 with eight of those occurring in 2015 and one in each of the other years. In eight of the crashes, the self-driving cars were stopped or traveling at less than 5 mph; the cars were traveling more than 5 mph in the other three crashes.

All 11 crashes involved other motor vehicles while only 68% of conventional vehicle crashes involved other vehicles and 15.8% involved fixed objects, 14% involved non-fixed objects and 2.2% were non-collision events. Eight of the 11 crashes (73%) came when the self-driving car was rear-ended, compared with 48.3% of rear-end crashes for conventional vehicles. No crash involving a self-driving vehicle was a head-on collision.

There were no fatalities among the 11 crashes of self-driving cars and just two (18.2%) resulted in injuries. Some 28% of crashes of conventional vehicles involved injuries.

Perhaps the most telling observation is this:

Based on narratives supplied in the crash descriptions for the crashes occurring in autonomous mode, the self-driving vehicles do not appear to be at fault in any of the crashes that have occurred to date.

That is virtually certain to change as more autonomous vehicles take to the road, but this first look at crashes provides some hope that serious crashes might become rarer even if they won’t disappear completely.

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