The Rand study noted that self-driving vehicles have the potential "to significantly" reduce the 32,000 fatalities and more than 2 million injuries that result from auto crashes every year. More than 90 percent of those crashes are caused by human errors, the study points out.
"Autonomous vehicles are never drunk, distracted or tired," factors which are "involved in 41 percent, 10 percent and 2.5 percent of all fatal crashes, respectively," the study found.
And self-driving cars may be safer than human drivers in other regards, because they don't suffer from blind spots, and have better decision-making and better execution of steering, braking and acceleration, the analysis said.
But the study also said that "autonomous vehicles might not eliminate all crashes."
It noted that bad weather and "complex driving environments" present challenges for self-driving cars, and such vehicles "might perform worse than human drivers in some cases."
"There is also the potential for autonomous vehicles to pose new and serious crash risks," because of their exposure to cyberattacks, for example, the study said.
While self-driving vehicles offer "enormous potential benefits," they also present "enormous potential risks," the study said.
Rand senior statistician Susan Paddock, a co-author of the study, noted that "the most autonomous miles any developer has logged are about 1.3 million miles," which was done by Google's fleet of self-driving cars. And that "took several years," which "does not come close to the level of driving that is needed to calculate safety rates," Paddock said.
"Even if autonomous fleets are driving 10 million miles, one still would not be able to draw statistical conclusions about safety and reliability," Paddock said.