The National Highway Traffic Safety Administration is handling a full load of safety recalls and investigations these days, including the investigation of a fatal crash involving Tesla’s Autopilot system. On May 7, a man was killed on a Florida highway when his Tesla Model S—with Autopilot activated—drove under an 18-wheel semi-truck turning in front of the vehicle. NHTSA commenced its investigation of the incident seven weeks later.

After the announcement of the investigation, Tesla published a blog post referring to the fatality as a tragic loss, but emphasized that it was the first fatal crash in more than 130 million miles driven with Autopilot activated. For comparison, Tesla explained that a fatal crash occurs in the US approximately every 94 million miles and worldwide approximately every 60 million miles. Fatality rates aside, Tesla owned the fact that its Autopilot system failed to observe the semi-truck and apply the brake because the trailer’s high ride height, white-colored side, and positioning across the road presented “extremely rare circumstances” making it difficult for the Autopilot to distinguish the trailer from the brightly lit sky in the background.

News of the fatal crash and announcement of the investigation comes as NHTSA is preparing to release new guidelines regarding the deployment and operation of autonomous vehicles later this month. Opponents to the rapid deployment of automated vehicle technology have been outspoken in response to the crash.

“The Administration should slow its rush to write guidelines until the causes in this crash are clear, and the manufacturers provide public evidence that self-driving cars are safe. If a car can’t tell the difference between a truck and the sky, the technology is in doubt,” said Carmen Balber, executive director of Consumer Watchdog.

To date, most of the evidence has indicated NHTSA’s support of regulations that will generally avoid interfering with the development and deployment of autonomous vehicle technology. However, NHTSA’s Administrator, Mark Rosekind, has consistently made it clear that vehicle safety is the agency’s top priority. During his comments at an autonomous vehicle conference in Novi, Michigan last month, he explained that self-driving vehicles must be at least twice as safe as human drivers.

We need start with two times better,” said Mr. Rosekind. “We need to set a higher bar if we expect safety to actually be a benefit here.

It is unclear when we will reach the point where self-driving vehicles will be considered sufficiently safe by NHTSA, or whether heightened scrutiny of self-driving vehicle technology prompted by the crash will cause NHTSA and other regulators to slow down the deployment of self-driving vehicles. But the autonomous vehicle guidelines that NHTSA has promised to release later this month may help to answer these questions.

Abbi M. Jankowski is co-author of this article.