Current methods being used to test driverless cars wont definitively prove their safety, according to a report by US think tank RAND.
The RAND report states that autonomous vehicles would have to be driven hundreds of millions of miles and, under some scenarios, hundreds of billions of miles to create enough data to clearly demonstrate their safety.
“Our results show that developers of this technology and third-party testers cannot drive their way to safety,” said co-author of the study and a senior scientist at RAND, Nidhi Kalra. “It’s going to be nearly impossible for autonomous vehicles to log enough test-driving miles on the road to statistically demonstrate their safety, when compared to the rate at which injuries and fatalities occur in human-controlled cars and trucks.”
RAND believes alternative testing methods must be developed to supplement on-road testing, but even then it may not be possible to fully establish the reliability of autonomous vehicles prior to making them available for public use.
Under even the most-aggressive test driving assumptions, it would take existing fleets of autonomous vehicles tens and even hundreds of years to log sufficient miles to adequately assess the safety of the vehicles when compared to human-driven vehicles.
Alternative methods of testing might include accelerated testing, virtual testing and simulators, mathematical modelling, scenario testing and pilot studies.
“Even if autonomous vehicle fleets are driven 10 million miles, one still would not be able to draw statistical conclusions about safety and reliability,” said co-author of the study and senior statistician at RAND, Susan M. Paddock.
According to the National Highway Traffic Safety Administration, more than 90% of automobile crashes are caused by human errors such as driving too fast, being drunk at the wheel, as well as distraction and fatigue.
But despite the high number of crashes, injuries and fatalities from human drivers the rate of human errors is low in comparison with the number of miles that people drive.
Americans drive nearly 3 trillion miles every year, according to the Bureau of Transportation Statistics. In 2013, there were 2.3 million injuries reported, which is a failure rate of 77 injuries per 100 million miles driven.
The 32,719 fatalities recorded in 2013 amount to a failure rate of about 1 fatality per 100 million miles driven.
“The most autonomous miles any developer has logged are about 1.3 million, and that took several years. This is important data, but it does not come close to the level of driving that is needed to calculate safety rates,” said Paddock.