https://www.cnbc.com/2018/05/02/effectiveness-of-tesla-autopilot-was-not-assessed-nhtsa.html

The U.S. National Highway Traffic Safety Administration (NHTSA) said Wednesday that a prior investigation into Tesla's semi-autonomous "Autopilot" self-driving system did not assess the "effectiveness" of the technology.

In 2017, NHTSA closed a probe into a May 2016 fatal crash involving a driver using the system and cited data from the automaker that crash rates fell by 40 percent after installation of Autopilot's Autosteer function. Tesla has repeatedly cited the statistic in defending the system.