Autonomous vehicles have the ability to make traffic move smoother. But first, they need to be more widely deployed. And that means creating the right regulations for the right cars.

At least 20 percent of the vehicles on the roadways will need to be autonomous in order to realize the traffic operational gains that come with connected vehicles, according to new research from Carnegie Mellon University.

“One of the goals of our work was to quantify the amount of AVs [autonomous vehicles] under which we would begin to realize these traffic and congestion benefits; surprisingly, we found that only 20 percent are needed,” said Carlee Joe-Wong, one of the authors of the report, Mixed-Autonomy Era of Transportation: Resilience and Autonomous Fleet Management. “And that 50-ish percent AVs was sufficient for realizing most of the gains.”