Is a head-up display a useful safety tool or one more distraction? Here’s where the HUD is a godsend: It’s been a long day on the road and nightfall approaches. Interstate 81 through Pennsylvania is a maze of converging and crossing roads where you can’t always stay in the middle lane to stay on the main road. If you check your navigation display, it can only be for a fraction of a second because of the traffic and construction barricades. Here (photo above) the roadway splits equally left and right and your destination is 25 miles outside New York City, but which way to bear, left for “New York”? Right for “Scranton”? In BMW’s new X3 SUV with a full-color HUD, a display floating over the dash shows your path is to the right. That’s safety.
Head-up displays (HUDs) have been around in cars here for two decades and in fighter aircraft since the 1960s. Now the HUD is making a comeback. General Motors, which used bulky, heat-producing CRTs to create some of the first US HUDs, just came back into the market. Other German automakers have offered HUDs, as does Lexus. (Some offer them in home markets only.) BMW has been the standard bearer, offering HUDs for more than a decade with monochrome HUDs, partial-color HUDs using a 128-by-128 pixel Osram LED array that created a red-orange-green display, and now full-color. At the same time, the resolution has improved to VGA (640×480) and beyond, good enough that it could be your only instrument panel on a future car. That’s enough resolution for a moving map or (let’s not go there) texts, tweets, or email headers.
A challenge to the adoption of the HUD, beyond cost, is driver distraction: not whether it reduces distraction, but possibly whether it causes. Seriously. Automakers scoff and say it’s clear that a head-up display (that’s the proper spelling, pilots say, not heads-up display) reduces driver distraction. But in an era when NHTSA and the NTSB have concerns that everything done in the car could be distracting, it’s possible they could aim their rulemaking gunsights at HUDs. (The top two distractions? Bee in the car and dropping a lit cigarette in your lap.)
People who haven’t driven a HUD-equipped car often ask: “But isn’t it distracting, with all that information getting in your line of sight?” In a word: no. For the first hour or day, a HUD is a wonderful toy to admire and you think of the gadget, not the information it imparts. Then you settle down and appreciate how easily the most useful information appears to float just above the hood of the car, a bit below your line of sight. On a BMW, that’s speed, cruise control setting, adaptive cruise control settings (following distance and radar lock on a car in front), tachometer (some sports models), and navigation arrows. Audio information is coming.
In Europe, BMW has developed vision cameras that can even read temporary or permanent road signs as well as overhead signs. They can project the temporary speed limit or other hazard information onto the HUD, as shown here. This was a Europe-first technology because Europeans used common signage; in the US different states used different signs. Technology apparently hasn’t figured a way to deconstruct the meaning of a rectangular sign the says “Speed 65 Limit Trucks 55 Minimum 40.”
General Motors pioneered HUDs in the US around 1990 with a CRT system (bulky, hot) that projected night vision images onto the windshield. It wasn’t clear if the buyer takeaway was “jet-fighter technology” or “assisted vision for old folks” because it was fitted to cars sold to the over-60 set. Now it’s back with a more compact system that “projects vehicle speed, engine speed [um, that’s called the tachometer], audio system settings and other valuable information.” More importantly, it’s affordable. Where BMW’s HUD runs $1,300, it’s a $1,000 technology package option. On the $40,000 GMC Acadia SUV, for instance, the tech package comprises the HUD, xenon headlamps, and — this is technology? — cargo area audio controls so you can crank up the volume at tailgate parties without walking so far. That suggests the price of the HUD alone would be less than $500, at least for monochrome HUDs.
Current HUDs all use a light source such as an LED array (possily OLEDs in the future) in the dashboard behind the instrument panel. It bounces off one mirror in the dash, then a second, silvered film at the base of the windshield. The driver sees through the mirrored patch as well as seeing what’s on the mirrored patch. It can be adjusted up or down to adapt to driver height as well as personal preference for how high it floats, but always in the lower half of your vision.
BMW in the past was reluctant to put something so frivolous as audio information in the HUD, but this also was the company that had to be dragged kicking and screaming into the cupholder era. (It does have Google Search in moving cars.) Now, even BMW is migrating audio information into its HUD, so that when a user moves the small scroll wheel on the steering wheel to shift among stations or audio selections, the current music choice shows in the HUD. BMW says it has added the music information to HUDs on the 5 Series and 6 Series. At the same time, it has migrated the HUD downmarket to vehicles such as the next-generation BMW X3, downmarket here meaning a vehicle with a base price around $40,000. The X3 starts at $38,000 but you can push it to $58,000 with sport, dynamic handling, premium audio, and technology packages.
GM has grander plans for HUDs. In conjunction with college research teams, it’s building a system that would use infrared sensors for enhanced vision systems. Ultraviolet lasers would paint the head-up image onto the windshield. Thomas Seder, a group lab manager at GM R&D, says, “Let’s say you’re driving in fog. We could use the vehicle’s infrared cameras to identify where the edge of the road is and the lasers could ‘paint’ the edge of the road onto the windshield so the driver knows where the edge of the road is.”
One advantage of the HUD is the projected display is farther away from your eyes. So it’s easier to make out the information if you need reading glasses and aren’t wearing them. That affects the majority of the population over 40. What BMW does for $1,300 and GM could do for $500, Honda does for no extra cost. On the Honda Civic, it embeds a second instrument panel at the base of the windshield, about three feet away from the driver’s eyes, for enough away that most baby boomer eyes can read it perfectly. Other automakers such as Ford say they’re studying this as a cheaper-than-HUD, almost-HUD system for providing information without having to glance so far down or over at the center stack or instrument panel.