A drawing of a dashboard and windshield as designed by engineers at Visteon. (Handout/Courtesy of Visteon)

One of the automotive world’s newest, buzziest upgrades was once offered only for trained jet pilots: heads-up displays, projecting a buffet of colorful information on that once-sacred place of clarity, the car windshield.

Touted at this week’s Consumer Electronics Show, the icon-rich displays have been installed by carmakers and tech startups as showcases for details on speed, directions, even cellphone notifications like text messages and Facebook alerts.

Carmakers argue the displays are a safeguard against fumbling with smartphones and other distractions. But safety advocates say the gadgets actually make the problem worse, by diverting drivers’ attention from the road ahead. And as carmakers compete for increasingly tech-minded buyers, some worry the displays will lead to even more dangerous roads.

“The manufacturers of these heads-up displays, none of them have said that any of their conclusions or assertions of safety are supported by any scientific evidence,” said Joel Feldman, an attorney and president of End Distracted Driving, whose daughter, Casey, was killed by a distracted driver in 2009.

“They’re taking the conclusion that if you’re looking straight ahead, instead of down in your lap, it’s safe, no matter what you’re doing with your mind. The science says that’s not true at all.”

Displays that sprinkle full-color warning signs and animated blips across a driver’s windshield are already offered in select models from carmakers as diverse as Hyundai, Volvo and BMW. But as the technology becomes cheaper and easier to install, analysts say the displays could become increasingly ubiquitous, even before any definitive study determines their safety on the road.

At the electronics show in Las Vegas, carmakers have offered up vivid, high-definition displays as key upgrades for their latest models, with promises of new features and information to come.

Volvo showcased a system that will send bright alerts to city drivers when they’re about to collide with cyclists. BMW drivers can use their display to change the radio, and be shown a bright orange “speed warning” on their windshields if they drive over a preset limit. And when Hyundai’s 2015 Genesis scans nearby cars and calculates the likelihood of an upcoming crash, the car’s display will project multicolored warning symbols across the windshield as alerts.

Newer, splashier displays are on their way. Jaguar Land Rover has advertised a “360 Virtual Urban Windscreen” that would fill the windshield even further, highlighting pedestrians, suggesting points of interest and even displaying a “ghost car” that drivers would be expected to follow for directions.

Carmakers are not alone in pushing to expand the technology. GPS maker Garmin sells a system that beams simple directions onto a small dashboard-mounted pane for $105; one Amazon reviewer said it “helps me stay 100% safe!”

Another big push for windshield displays has come from a San Francisco tech startup called Navdy, which offers a $299 heads-up display that the company says “feels like driving in the future.”

A tiny projector beams turn-by-turn directions, Twitter notifications and other social-media notes onto a screen above the steering wheel with an intensity that is 40 times brighter than an iPhone, the company said.

The system also watches for driver gestures — swipe left in the air to answer a call, swipe right to dismiss a notification — and listens for voice cues to write texts or tweets, which can also be displayed on the screen like an in-car version of Google Glass.

In a promotional video, a driver calmly navigates through San Francisco roads and a flood of digital distractions, likening the system to what pilots rely on during landings: “You hear that?” he says. “Pilots use it. It’s safe.”

The company, which did not respond to messages Tuesday, has said it sold a device every minute for the first 24 hours of launch, hitting $1 million in sales within a week of pre-orders in August. The first units are expected to ship this year. Another startup, Skully, offers a heads-up display in a motorcycle helmet.

Not all automakers agree on how much is too much to display. Though Mercedes-Benz this year began offering heads-up displays in three of its coupes and sedans, touting high-definition readouts and “special windshield glass,” Mercedes spokesman Christian Bokich said the current readouts offer little more than a speedometer — similar to what was offered in a late ’80s Oldsmobile Cutlass Supreme.

The technology “is not something we actively push,” Bokich said. “Simplicity is key, so it’s not a distraction. The more information you put on the screen, the more you’re going to confuse the customer. We don’t want customers to feel overwhelmed to the point they’re not comfortable driving their car.”

Heads-up displays, or HUDs, have been around since fighter pilots watched the skies through reflective gunsights during World War II. But even modern-day trained aviators can face issues with distraction. In 2004, NASA researchers said the “compellingness” of symbols and information on heads-up displays often diverted pilots’ focus, a problem they called “attention capture.”

Even after decades in the cockpit, the displays have never been so widely used by untrained consumers, or in so many cars on the road. The National Highway Traffic Safety Administration started research on heads-up technology and distraction last year, officials said, though their results have yet to be released.

Researchers say some simple displays of information in a driver’s field of view can be helpful. But as the displays begin to include more complicated information, much of it far from necessary from keeping the car on track, some said they could give drivers a kind of “inattentional blindness,” or tunnel vision, when they should otherwise pay attention to the road.

“Just because someone has their eyes straight ahead doesn’t mean they’re seeing everything in their line of sight,” said Paul Atchley, a professor of cognitive psychology at the University of Kansas who has researched attention in 3-D spaces for the U.S. Army. “You get the illusion of paying attention to the road without the benefit of seeing what’s important.”

Some safety advocates scoffed at the comparison to heads-up displays in commercial jets, which are primarily used during landings — by experienced pilots. As Jeff Larason, president of the Safe Roads Alliance, a distracted-driving advocacy group, said, “What a pilot does, with ongoing training, demands a very different experience requirement than what Aunt Judy has driving on the Beltway.”