When it comes to the safety of driverless cars, a little goes a long way.

Cars that drive themselves some or most of the time only have to be slightly better drivers than humans to slash the rate of fatal car crashes, according to a new study by the RAND Corporation, a nonprofit nonpartisan think tank based in Santa Monica, California.

“There’s a lot of hand-wringing around this question and a lot of conjecture,” said co-author Nidhi Kalra. “We what we found surprised us.”

Self-driving cars will never crash because their drivers are drunk, distracted, sleepy, or speeding, but they have their own set of problems, such as attacks by hackers or hardware or software snafus, researchers noted.

And yet using computer modeling, RAND researchers compared three scenarios: one where driverless cars were just 10 percent safer than human drivers, one where they were 75 percent better and one where they were “nearly perfect,” or 90 percent better.

In both short (15 years) and long-term (30 years) scenarios, more lives were saved by quickly adopting the driverless cars that were just 10 percent better, researchers found. The difference was “significant,” ranging from tens of thousands to hundreds of thousands of saved lives, researchers found.

In one model, autonomous vehicles that were 10 percent safer were introduced to the marketplace in 2035 and saved 600,000 lives over the following 35 years. By 2070, there would be 1.5 million car crash fatalities if the driverless cars were on the road, compared with 2.1 million fatalities that would occur if they hadn’t been introduced, researchers found.

“We couldn’t find a single scenario in which it makes sense to wait until the vehicles are perfect,” Kalra said. “Waiting doesn’t save lives, relative to being a little more aggressive.”

One reason: once the cars are in use, their technology will quickly improve in response to exposure to real-world scenarios that the cars’ developers wouldn’t foresee during simulations, Kalra said. One downside: There will undoubtedly be fatal crashes involving self-driving cars either way, which could create a backlash against the technology.

There are generally two schools of thought on when to allow driverless cars onto roads, Kalra said: Some feel the automated cars should hit the streets as soon as they are slightly better than human drivers, while others say the technology should be as close to perfect as possible.

There’s support for the former scenario: RAND’s study comes as auto fatalities have been on the rise. In 2016, 37,461 people were killed in car crashes, up from 35,092 in 2015, according to the National Highway Transportation Safety Administration.

Even so, drivers are only lukewarm about a driverless future. A 2016 survey by Kelley Blue Book found that most drivers (51 percent) would prefer to keep full control of their vehicle.