Drivers using partially automated driving systems lean toward distracting themselves from the road, according to a new study.

The study, from the Insurance Institute for Highway Safety, found that drivers checked their phones, ate or did other manual activities more often while using an automated driving system.

Over one month, the researchers studied how often drivers became distracted while using Volvo’s Pilot Assist program and Tesla’s Autopilot system.

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According to the researchers, drivers using Volvo’s Pilot Assist groomed, ate or fiddled with electronic devices at a dangerous clip. The study found that Volvo drivers were distracted around 30% of the time.

“We saw some differences in how the three groups used Pilot Assist, but we couldn’t say for sure they were related to the software changes,” IIHS Senior Research Scientist Ian Reagan said. “The takeaway for me was that the technology was linked to more distraction for all three.”

In studying Tesla’s Autopilot, the researchers focused on how many times drivers triggered the car’s alert systems. The electric vehicle firm’s automated driving program requires that drivers keep their hands on the wheel. If the car detects that the driver isn’t paying enough attention to traffic, it will issue escalating warnings until finally locking the driver out of the feature for a limited time.

Over 1,200 miles, the researchers recorded 3,858 alerts triggered by a driver’s inattention. They said most alerts ended before they escalated, with only 16 persisting until the driver was locked out of the system.

The study comes as regulators look into self-driving cars and automated driving systems. Tesla is under investigation by the National Highway Traffic Administration for possible safety violations in its Autopilot and Full Self-Driving programs. The agency also is probing over two dozen collisions involving Waymo, Google’s self-driving taxi subsidiary.