The National Highway Traffic Safety Administration is investigating a crash involving a Tesla Model S that allegedly happened while Autopilot was engaged.

Autopilot, for those not aware, is made up of a semi self-driving features that include adaptive cruise control and automatic steering/lane keep. On Monday, the black Model S slammed into the rear of a firetruck in Culver City, Calif. that had stopped on the freeway after responding to an accident. The EV buried its nose under the rear of the truck, totalling it, but no one was hurt. The driver allegedly told police the vehicle’s Autopilot was engaged at the time of the accident, which has now prompted the NHTSA investigation.

This issue highlights a growing and concerning trend with partial self-driving systems. These early semi-autonomous systems still require driver input to operate safely, but many consumers seem to think they are fully self-driving and don’t pay proper attention while using them. The California Highway Patrol recently responded to a call for a driver passed on the Bay Bridge in a Model S. The driver’s blood alcohol level was two times the legal limit, but they told the CHP it was okay because the car was autonomous.

In response to these incidents, Tesla has said Autopilot is “intended for use only with a fully attentive driver.” It seems the message isn’t getting through to some consumers, however.

Bloomberg, ARS Technica

Photo courtesy of Culver City Firefighters on Twitter.

This article originally appeared at AutoGuide.com.