Self-driving car advocates often note that more than 90 percent of serious accidents result from driver error, and thus estimate that autonomous cars will reduce fatalities by 90 percent. Indeed, in 2008 a National Highway Traffic Safety Administration (NHTSA) study of crashes between July 2005 and December 2007 found that 5,096 were caused by driver error, while just 130 were caused by vehicle failure and 135 were caused by the weather.
After some adjustments, NHTSA concluded that 93 percent of accidents can be attributed to driver error. So it seems reasonable to conclude that self-driving cars will save more than 31,000 lives per year (i.e., about 93 percent of the 33,560 fatalities suffered in 2012).
Not so fast, says a group called the Casualty Actuarial Society. It took a close look at NHTSA’s 2008 study and found that “49% of accidents contain at least one limiting factor that could disable [autonomous vehicle] technology or reduce its effectiveness.” That means self-driving cars will only reduce fatalities by about half, not 90 percent. While 16,000 lives saved per year is nothing to complain about, there’s a big difference between 16,000 and 31,000.
