Car companies battling for their share of $2 trillion in annual global auto sales increasingly lean on shiny tech that takes over some of the driving from humans.

Boasting names such as Autopilot, Super Cruise and ProPilot Assist, these systems — whose radar and cameras are the building blocks of self-driving cars — are part of a growing effort by manufacturers to woo with computing power rather than horsepower.

But on the heels of two Teslas that crashed while on Autopilot, automakers find themselves increasingly torn between hyping the tech and warning owners about its limitations.

"It's on us to educate people about what's allowable and what's not allowable," says Andy Christensen, lead engineer on Nissan's ProPilot Assist. "We don't want drivers to be overly confident. (The tech) is there to assist you, it's not driving for you."

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More than a dozen manufacturers from Audi to Volvo now offer so-called ADAS options (Advanced Driver Assistance Systems) on their cars. As questions resurface about whether the efficacy of such driving aides lulls drivers into complacency, automakers pack manuals with disclaimers, provide in-car audio and visual warnings, and direct salespeople to remind customers that such features should not be abused.

But the magical perception of driver-assist tech — hammered home in their names, advertising and even executive comments — can obscure an operational reality that demands drivers constantly monitor the self-driving system and sometimes be prepared to take over in a split second.

Consider Nissan's new television ad for ProPilot Assist. It opens with a Star Wars spaceship threading the needle between two enemy cruisers, then cuts to a woman driving a Rogue SUV on a bridge as it heads between two semi trucks.

"I've got this," she tells her passenger, and then the vehicle is shown driving itself between the trucks as her hands hover just above the steering wheel — but not on it. The car is using its sensors to detect the lane markings and center the car, but frequent input to the wheel by the driver keeps the system on.

When Mercedes-Benz introduced its 2017 E-Class, it touted the car's tech chops in a TV spot that asked whether the world was ready for a vehicle "that can drive itself."

Although the commercial offered disclaimers at the bottom of the screen — "Vehicle cannot drive itself, but has automated driving features" — Mercedes quickly pulled the ad in response to criticism it was misleading to consumers.

Cadillac's Super Cruise system is billed in ads as "the world's first true hands-free system for the highway ... no need to tap the wheel to show you're still there." But, the ad quickly adds, "that doesn't mean you can check out."

The system uses a head-tracking camera to detect whether the driver is looking away from the road ahead. If necessary, the top of the steering wheel will flash red, alerts will sound and the seat vibrates to get the driver to take over. Super Cruise only works on pre-mapped highways, but on such roads ads show hands in laps.

And not long after Tesla launched its boldly named Autopilot system in 2015, CEO Elon Musk declared "it's probably better than a person right now," adding that it soon would "drive virtually all roads at a safety level significantly better than humans."

Musk more recently said Autopilot will "never be perfect," and after two recent crashes, his company has issued a litany of statements reminding drivers of their responsibility when engaging Autopilot.