– Tesla's partly automated driving system steered an electric SUV into a concrete barrier on a Silicon Valley freeway because it was operating under conditions it couldn't handle and because the driver likely was distracted by playing a game on his smartphone, the National Transportation Safety Board (NTSB) has found.

The board made the determination Tuesday in the fatal crash, and provided nine new recommendations to prevent partly automated vehicle crashes in the future. Among the recommendations is for tech companies to design smartphones and other electronic devices so they don't operate if they are within a driver's reach, unless it's an emergency.

Chairman Robert Sumwalt said the problem of drivers distracted by smartphones will keep spreading if nothing is done.

Much of the board's frustration was directed at the National Highway Traffic Safety Administration (NHTSA) and to Tesla, which have not acted on recommendations the NTSB passed two years ago. The NTSB investigates crashes but only has authority to make recommendations. NHTSA can enforce the advice, and manufacturers also can act on it.

But Sumwalt said if they don't, "then we are wasting our time. Safety will not be improved. We are counting on them to do their job."

For Tesla, the board repeated previous recommendations that it install safeguards to stop its Autopilot driving system from operating in conditions it wasn't designed to navigate. The board also wants Tesla to design a more effective system to make sure the driver is always paying attention.

If Tesla doesn't add driver-monitoring safeguards, misuse of Autopilot is expected "and the risk for future crashes will remain," the board wrote in one of its findings.

Tuesday's hearing focused on the March 2018 crash of a Tesla Model X SUV, in which Autopilot was engaged when the vehicle swerved and slammed into a concrete barrier dividing freeway and exit lanes in Mountain View, Calif., killing Apple engineer Walter Huang.

Just before the crash, the Tesla steered to the left into a paved area between the freeway travel lanes and an exit ramp, the NTSB said.

It accelerated to 71 mph and crashed into the end of the concrete barrier. The car's forward collision-avoidance system didn't alert Huang, and its automatic emergency braking did not activate, the NTSB said.

Also, Huang did not brake, and there was no steering movement detected to avoid the crash, the board's staff said.

NTSB staff members said they couldn't pinpoint exactly why the car steered into the barrier, but it likely was a combination of faded lane lines, bright sunshine that affected the cameras, and a closer-than-normal vehicle in the lane ahead of the Tesla.