Tesla robotaxis are not necessarily operating without a human in the loop, even its small number of unsupervised robotaxis that lack safety operators. If you’re a self-driving car fan, that reflects a deflating fact of life about the current state of autonomous vehicles: the companies operating them still don’t trust them on the roads without occasional button pushes from a flesh-and-blood human sitting at a desk somewhere.

But Tesla appears to be unique among its competitors when it comes to the extent to which its vehicles occasionally rely on humans. That is to say: they occasionally surrender control to them completely.

Karen Steakley, director of public policy and business development at Tesla, recently divulged this in a letter to Senator Ed Markey, a Democrat representing Massachusetts (as first reported by Wired). Human operators, Steakley wrote, “are authorized to temporarily assume direct vehicle control as the final escalation maneuver after all other available intervention actions have been exhausted.”

Competitors like Waymo say they allow humans to play a role in the operation of a vehicle on the road, but a more limited one, and they take great pains to make this distinction. Waymo’s description of what went wrong last year when its vehicles seemed to have a widespread meltdown during a blackout in San Francisco touched on this, for instance.

The issue involved a large number of Waymo vehicles encountering four-way stoplights that were blacked out, and sending an unmanageable number of confirmation requests to human workers with Waymo’s “fleet response” division, which we now know is largely based in the Philippines.

According to Waymo’s public relations materials online, rather than, say, “steering” the vehicle remotely, perhaps with a joystick, fleet response workers see camera feeds and 3D representations of the Waymo vehicle’s position within its environment and give feedback. They might simply have to click an answer to a question like Is the street I’m trying to turn onto closed? Or they might suggest a new course of action for getting out of a jam, like pulling into a driveway to let others pass.

They do this in a way that is a bit like telling a unit what to do in a real-time strategy video game, except Waymo insists that the “Waymo Driver”—the hardware and software system that drives the car—can refuse the human suggestion, meaning it never surrenders executive control.

Steakley makes it pretty clear that Tesla lacks Waymo’s compunctions about seizing the car’s autonomy entirely. Tesla employs “remote assistance operators” (RAOs) in Austin, Texas and Palo Alto, California in order to “promptly move a vehicle that may be in a compromising position,” she told Markey in the letter. A human might take “temporary control of the vehicle,” and remotely move it up to 10 miles-per-hour, she explained.

This only happens “if direct access is granted by the Tesla [automated driving system].” Though she also notes that if a rider requests help, they may end up communicating with a Tesla RAO “via bidirectional audio.”

RAOs must also, according to Steakley:

• have a “valid U.S. driver’s license for a minimum of 3 years”
• “maintain a license and clean driving record throughout their employment.”
• “undergo criminal background and Motor Vehicle Record checks”
• “pass a U.S. Department of Transportation drug test”

Markey issued a report Tuesday, after receiving similar letters in response to  questions about remote operation in these vehicles not just from Tesla and Waymo, but also five other competitors. Markey believes the responses reflect a “patchwork of safety practices across the industry, with significant variation in operator qualifications, response times, and overseas staffing, all without any federal standards governing these operations.”

Gizmodo reached out to Tesla and Waymo about these letters, and about Markey’s report. We will update this article if we hear back.