To keep drivers' eyes on the road, cars are getting a third display to project information: the windshield

Cars are running out of screens. The dashboard is a jumble of numbers, icons, indicator lights, and gauges. In some vehicles, the display built into the center console is bigger than our televisions in certain rooms at home. But drivers' and passengers' appetite for more information isn't subsiding, so the dashboard and entertainment console are about to get a companion: the windshield.

At the Detroit auto show, which runs until Jan. 25, you'll find demonstrations of cars with built-in projectors displaying speed, range, turn-by-turn directions, and other crucial data along the bottom of the windshield. Head-up displays—developed to keep fighter pilots' eyes on the sky rather than on the instruments in the cockpit—have existed in some form for cars since at least the 1980s, but they've mostly functioned as a novelty for high-end clientele. In the past year, however, HUD technology has made its way into some Mazdas and Priuses as a way to manage information overload for everyday drivers.

Automakers have been adding a flood of information designed to keep drivers safe—some requested by customers, others mandated by governments—but it risks having the opposite effect. As weird as it sounds, projecting text and graphics onto the windshield may be less distracting to drivers than forcing them to look down at cluttered in-car screens—or worse, their mobile phones. A HUD, which sits within the driver's line of sight, would be free of "check engine" and "change oil" lights, and only display the alerts a driver might need at any given moment. Hyundai, Toyota, and General Motors expect the HUD to go mainstream very soon.

"It's about keeping the driver's eye on the road, " says Carson Grover, a product planner at Hyundai Motor America. "For a long time, we thought a HUD was kind of a gimmick. Now we see this as a technology that's going to get more important over time."

Hyundai’s augmented-reality head-up display could help identify pedestrians and pets.

Hyundai Motor America

Hyundai offers HUDs as an option on its luxury models, including the Equus and Genesis, and the company plans to eventually build the feature into more affordable models, Grover says. Some Toyota Prius, Mazda3, and Mini (owned by BMW) models are among the mass-market vehicles that offer HUDs today. In 2010, people bought just 380, 000 car HUDs worldwide, meaning about 0.5 percent of vehicles sold that year were equipped with the feature, according to market researcher IHS. This year, that total is expected to jump to 2.3 million, and by 2021 it could reach 11 million, according to IHS analyst Mark Boyadjis.

"That's a potentially conservative number as we've been hearing a lot in the last six months from you-name-it about HUDs, " Boyadjis says. "It was a very small party. Now, if you're a tier-one supplier in automotive electronics, you're looking at HUD because it's such a growth market."

Like any new technology, its history can be traced back to a Tom Cruise movie. In 1988, two years after Top Gun introduced the technology to a mainstream audience, GM equipped an Oldsmobile Cutlass Supreme with a rudimentary HUD that projected the car's speed onto a screen. Doesn't it take your breath away?

Over the years, different variations of the HUD have appeared in some Corvettes, Nissan's 240SX, and a few other vehicles. The gadget didn't catch on. It was expensive and repeated the same limited data points that were already on the dash—usually speed, revolutions, and gas levels.