Coming soon to vehicles at a dealership or driveway near you: head-up-displays (HUDs). Imagine seeing the speed limit, your next turn or the optimal distance to be from the car in front of you projected onto your front windshield, the same one you look through to steer the car. This latest technology is meant to make us more aware and conscientious behind the wheel.

Or will it turn us into even more-distracted drivers?

HUDs are already available on some Audi, BMW, Lexus and Cadillac models. If you’re shopping for a new high-end vehicle, here’s what you should know about this latest feature.

Related: Can’t Stop Texting While Driving? This Device Is for You

A safety plus or minus?

The goal of HUDs is to make driving safer by displaying important information directly in our field of vision so we don't have to look down and take our eyes off the road. According to the BMW website, “The BMW Head-Up Display projects relevant driving information directly into the driver’s line of sight. This allows him to process it up to 50 percent faster and keep his attention where it belongs — on the road.”

It sounds good in theory, but how well does it work in practice?

Researchers at the University of Toronto conducted a study to find out how effective we are at focusing on multiple streams of information beamed in front of our eyes.

Department of Psychology professor Ian Spence and his students Yuechuan Sun and Sijing Wu conducted two computer simulations. In the first, participants looked at a screen that flashed a number of randomly arranged circles. They were asked how many they saw. Sometimes a square was also shown.

When the square appeared, people missed it about one in 15 times on average. When even more circles were shown on the screen, the square-spotting accuracy dropped to one in 10, suggesting that the more stimulus that appears before our eyes, the worse we are at paying attention to it all.

Related: Samsung's Safety Truck Lends a Hand to Drivers

In the second test, a random shape (a triangle, square or diamond) was shown among the circles and participants were asked to identify when they saw it and what shape they saw. Again, when there were more circles on the screen — which would translate into more data being broadcast by an HUD — the participants were worse at identifying the shape or even noticing it at all.

“Observers made both judgments more slowly when the shape appeared among the spots by as much as 200 percent,” said Spence. “The two visual tasks interfered with each other and impaired both reaction speed and accuracy."

Apparently we’re not very good at focusing on multiple things at once. What does this mean for HUDs? "This innovation has the potential to make operating vehicles safer but our data suggest that there are significant concerns regarding driver distraction," the researchers write, although they acknowledge that more study is needed to verify this.

Driving with an HUD would mean paying attention not only to what's on the road but also to competing information sets on the windshield. “It would be necessary to distinguish, for example, between warnings of a collision and a recommendation to make a turn,” said Spence to the University of Toronto News. “Otherwise competing warnings may be more dangerous than no warning at all.”

Of course, this may all become a moot point in the next decade, as another automotive technology begins to come online: self-driving cars. When they're commercially available, we'll likely be able to sit back, relax and watch a movie beamed onto our windshields, safe in the knowledge that the computers driving us can't be distracted by a text message popping up onto our screen.

Related: How to Make Your Next Car Safer

Michael Franco is a science and technology writer who secretly wishes he was an astronaut. His work has appeared in CNET, HowStuffWorks.com and Discover Magazine.