"Sensing what's around you versus understanding it [are] vastly different," said Lexus VP Mark Templin, waxing philosophical about the company's so-called advanced active safety research vehicle — "AASRV" for short — at a dimly-lit CES event early this week.

From the unapproachable, awkward name, you'd probably never guess that the AASRV is actually a self-driving car, every bit as autonomous, advanced, and buzzworthy as the ones Google has been driving around California for the past several years. And that's just the way Lexus wants it: as the legal and ethical challenges of these vehicles cast an ever-growing pall on the research arm of the auto industry, carmakers are quick to play down the capabilities of the self-driving car and play up the responsibility of the driver. "The driver must be fully engaged in the operation of the vehicle at all times," Templin cautioned.

"We must combine the judgment of humans with the precision of machines, and that takes time."

It's not just the threat of a hypothetical lawsuit over a misbehaving autonomous car of the future that has Templin keeping his language in check. Lexus, parent company Toyota, and other carmakers represent one of the most heavily-regulated industries on the planet; there seems to be a broad recognition among the brands that it's going to take an enormous amount of lobbying — perhaps an overhaul of the entire way that departments of transportation think about cars — in order for these cars to be broadly legal.

At a roundtable on automotive technology this week, Audi's chief engineer of electronics Ricky Hudi was asked whether technology, legislation, or litigation would be most likely to hold back the development of the self-driving car. "The second one," he said without a hint of hesitation. Wolfgang Dürheimer, the ex-Bentley and Bugatti chief who leads Audi's R&D efforts, later lamented the United States' overwrought transportation laws, noting that it took an enormous amount of effort to simply get a sweeping strip of lights approved for use as a turn signal. The company's upcoming "Matrix" lighting system, designed to vary the intensity of the headlights in response to oncoming traffic as a safety measure, won't be legal here, either. Dürheimer went so far as to plead with members of the media in attendance to help publicize the pitfalls of the bureaucratic nightmares that Audi and its competitors face. "It's really a pity that a lot of intelligent lighting systems that we already have on the road, we can't offer to customers in the United States," Hudi added.

And that's just lighting. What happens when you amplify the level of controversy by a thousand?

"Final responsibility rests in the hands of the driver."

It's still far too early to answer that, and in the interim, carmakers are playing it as safely as they possibly can. Audi, for instance, demonstrated a self-parking car this week — effectively a rudimentary form of autonomy — and it's expected to come to production vehicles in the coming years. It only works at a few miles per hour, and only in parking garages that have been specially outfitted with sensors and other equipment. Audi also says that it will introduce a traffic jam assist mode that will self-drive under 30 miles per hour, only in congested traffic, and only if you keep your hands lightly on the wheel. If you take them off for ten seconds or more, the system disengages.

In fact, neither Audi nor Lexus will commit to a truly autonomous vehicle at all, carefully choosing language in an effort to keep liability for mishaps firmly with the driver. "Piloted driving" was a favorite buzzphrase with Audi this week. "We support piloted driving. Final responsibility rests in the hands of the driver," Hudi said.

But despite the regulatory obstacles, self-driving cars seem inevitable. Lexus had been quietly working on the AASRV since 2008 before revealing it this week, and it certainly doesn't intend to let that research and development go to waste. "Step by step, we will build trust with society and governments so that vehicles will be allowed to perform more automated tasks," Templin said.

"We are not getting into competition with the robot industry."

But never expect to take a nap as your high-tech ride of the future whisks you cross-country. As Dürheimer said when I asked him when I'd be able to let the car do one hundred percent of the work, "we are not getting into competition with the robot industry."