In a hearing Tuesday, Feb. 25, that stemmed from a fatal crash involving Tesla's Autopilot driver-assist system, he said California highway agency Caltrans, the U.S. Department of Transportation and the automaker had not yet provided responses to questions from the NTSB regarding the crash, which killed Walter Huang. Nearly two years have passed since the March 23, 2018, crash, and Sumwalt's frustration was palpable.

"How we effect change is through our recommendations becoming implemented, and it's, frankly, disheartening that these are not being responded to," he said.

Tesla's lack of cooperation comes as no surprise. In the early days of the investigation, the NTSB revoked the company's status as a party to the probe after the company released select data from the crash — data that suggested the driver was at fault. As last week's hearing proceeded, Elon Musk tweeted about ice cream and Kit Kats.

The surprise perhaps was the lack of response from other agencies. Tensions have simmered between NHTSA and the NTSB for some time, at least partially because NHTSA has relied upon voluntary guidance for automakers to handle the influx of new technology instead of promulgating regulations.

If that's happened largely behind the scenes, it spilled into stark view last week. The NTSB swung, and swung hard: Excoriating NHTSA's lack of standards for driver-assist systems that fall within the Level 2 automation definition. Calling out the federal regulator as putting industry profits ahead of safety. Identifying shortcomings in NHTSA's own investigations into Tesla's Autopilot system.