When Tesla unveiled the all-wheel drive Model S "D" variants last fall, it also promised a suite of automated features under the "Autopilot" name.

The company has been equipping production cars with the hardware needed for these features, but one of the most advanced ones has yet to roll out.

It's an autonomous passing function, which allows a driver to pass another vehicle simply by flicking a turn signal.

DON'T MISS: Tesla Reveals 'D' All-Wheel-Drive Model S, 'Autopilot' Feature (Oct 2014)

And it's that method of operation that could potentially allow Tesla to sidestep some legal questions surrounding autonomous operation.

The act of using a turn signal helps place the responsibility on the human driver rather than the computers, according to The Wall Street Journal (subscription required).

If the driver flicks the turn signal and engaging the autonomous passing system, the reasoning goes, he or she has made an assessment that such a maneuver can be safely completed.

Tesla Model S P85D, 2015 Detroit Auto Show

Tesla Model S P85D, 2015 Detroit Auto Show

That's supposed to remove any ambiguity about who is responsible if a car operating autonomously crashes.

While fully-autonomous cars probably won't make it into consumer hands for several years at least, liability has already become the subject of intense debate.

Several states including California, Nevada, Florida, and Michigan have explicitly legalized the testing of self-driving cars on their roads.

ALSO SEE: Elon Musk: Tesla Model S 'Ends Range Anxiety' With Smart Navigation, Trip Planner

Google was testing its fleet of autonomous cars on California roads well before the state's regulations were drafted, though.

The company recently acknowledge that its cars have had 11 accidents in California, although it claims all were due to human error.

There's still some time to debate the legality of Tesla's automatic passing function, though, because the company still hasn't announced a timeline for its launch.

Tesla Autopilot sensor system

Tesla Autopilot sensor system

Model S electric cars built since October have the necessary hardware for the system, and the software will arrive in one of Tesla's over-the-air updates.

The next update is scheduled for sometime this summer, but the automated feature may not be included in it.

MORE: Self-Driving Porsche Not Only More Fuel-Efficient, But Faster Than Humans Too (Nov 2014)

Tesla CEO Elon Musk has said the Autopilot system's capabilities could grow well beyond automated passing.

When the system was first announced, he said it will eventually be able to handle most driving duties on the highway, and come pick up an owner on private property.


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