On April 29, Jared Overton's Tesla Model S began to drive by itself – without Overton behind the wheel – and crashed into the back of a trailer, according to Salt Lake City NBC affiliate KSL. Tesla's records show that Overton’s Model S worked as designed after he initiated the car’s self-parking "Summon” mode. In the KSL report, Overton claims the car acted completely on its own.

After hearing Overton’s story, Consumer Reports decided to look into another possibility: Is it possible that a driver could launch Summon unintentionally? We tried the feature on our own Model S and found it was possible for the feature to be activated inadvertently by a hurried driver.

When Tesla initially added Summon to the Tesla Model S via an over-the-air update in early March, the car gained the ability to park itself without anyone in the vehicle. This self-parking mode could be activated by depressing the keyfob, or through Tesla’s smartphone app.

At the time, Consumer Reports was concerned that the feature didn’t require users to keep a finger on either the keyfob or smartphone screen throughout its operation. That meant the car could continue moving on its own if the user dropped the keyfob or accidentally shut down the app.

We communicated these concerns to Tesla, and the company responded quickly with a software update that limits the ways Summon could be activated. Tesla also added additional warnings for the user.

But Tesla’s update also introduced a new way to initiate self-parking. If a Model S owner deactivates “continuous press” in the vehicle’s settings, he or she can start Summon with a double tap of the Park button on the shift stalk. The car will then wait three seconds, and move either forward or backwards until it senses an object or is manually stopped by a press of the keyfob or one of the door handles.

We tried this ourselves at Consumer Reports’ auto test facility and found it was fairly easy to accidentally initiate Summon and walk away. For instance, a driver might press the Park button twice to make absolutely sure that the car was stopped. There are messages on the dash and in the large infotainment screen to tell the driver that Summon mode has commenced, and the hazard lights go on, but a driver in a rush might miss these messages and leave the vehicle.

Considering that the Model S moves silently and cannot sense all objects in its path, we urged Telsa to modify how this feature activates to a more intuitive manner – so that, once initiated, it is more clear to the user that the car has engaged self-parking mode.