The case was important because self-driving car makers were in a fluster as they wanted to automate more driving tasks without exposing themselves to increased liability risks.

Tesla Chief Executive Elon Musk, tweeted his praise for the National Highway Traffic Safety Administration, which did not order a recall and put the responsibility for the accident primarily on the driver, former Navy SEAL Joshua Brown.

US Transportation Secretary Anthony Foxx said that drivers have a duty to take seriously their obligation to maintain control of a vehicle. Tesla's Autopilot was limited because it could not detect a truck trailer that crossed the road in front of the victim's Tesla.

"The (auto) industry is going to have to be clear about what the technology does and what it is does not do, and communicate it clearly," Foxx said.

Jack Landskroner, a lawyer for Brown's family, said they plan to evaluate all the information from government agencies investigating the crash "before making any decisions or taking any position on these matters".

Legal experts said the agency's decision does not mean automakers would escape liability claims in cases where driver assistance systems fail. The agency said Brown "should have been able to take some action before the crash, like braking, steering or attempting to avoid the vehicle. He took none of those actions".

The agency said the truck should have been visible to Brown for at least seven seconds before impact. Brown "took no braking, steering or other actions to avoid the collision," the report said.