Head-Up Displays (HUDs) Put the Essentials in Your Line of Sight
By Bill Howard
Posted July 29, 2008, at 1 p.m.
One way to deal with driver distractions is to place, right in front of you, only the most important information — such as the fact that you're inadvertently going 5 mph over the limit — using a head-up display, or HUD. If it's important, the information is there, projected through the windshield. If it's not in the HUD, you probably don't need to know it, at least not right this instant.
How Head-Up Displays Work
Born of the military aviation world, in which systems project airspeed, compass heading, an artificial horizon, and a gunsight, vehicle HUDs use a small projector in the instrument panel that reflects the image off the base of the windshield in front of the driver. A windshield coating reflects the image so the driver can see the information, but you can still see through the windshield. The image is at the base of the windshield and appears to float just above the hood, so it isn't in the middle of your line of sight.
The focal point — how far away your eyes think it is — is somewhere between the front of the car and infinity. That means drivers who wear reading glasses (or who should wear them to see the instruments properly) don't have to refocus, as they might when glancing down to read gauges.
A dashboard knob adapts the elevation of the HUD system for drivers of different heights and also lets you decide how far up into your field of vision the image projects. Only the driver sees the information, not the passengers.
Helmet-mount HUDS are also available for motorcyclists and some race drivers.
HUDs are only on a handful of cars and cost about $1,200. But the price could come down, perhaps to $500, with higher volume production.
Information HUDs Project
What does the head-up display project in a typically passenger vehicle? It may include:
- Speedometer
- Turn signal indicator
- Navigation arrow, distance to next turn, and name of upcoming street or exit
- Cruise control or active cruise control speed setting and, for ACC, the desired following distance
- A check controls or check engine light
- On sporty cars in manual-shift mode, the current gear and engine speed
- Phone number or name of an incoming caller
- Sometimes the current radio station or song, which may appear for, say, 5 seconds after changing stations, then fade out.
In comparison, you don't really need to know whether your gas gauge reads half- or three-eighths full, or the exact engine coolant temperature. In there's a problem, the warning light will let you know. An important point to note about HUDs is that they are intended to complement and not obviate the need for other information (such as that provided through dashboard warning lights and indicators) already available to drivers.
Vehicles With HUD Options
If you want the head-up display on a current car, you're looking at a handful of premium vehicles. A $1,200 HUD on a $15,000 entry vehicle is a big chunk of money; on a $50,000 vehicle it's more like a rounding error.
Automakers with HUDs include BMW, Citroen, General Motors, Mercedes-Benz, Nissan/Infiniti and Toyota/Lexus. But not all of them offer HUDs in the U.S. Here, it's mostly BMW and General Motors.
BMW offers an HUD for $1,200 on its 5 Series, 6 Series, X5, and X6. BMW uses a bright, multi-color (but not full color) LED array projecting red, orange, yellow and green. GM has it on a handful of cars such as the Cadillac STS, where's it's part of the $3,500 "V8 performance collection" with head-up display, side blind zone alert, lane departure warning, adaptive cruise control and power sunroof.
GM was the first U.S. automaker with an HUD back in 1988; GM has used a CRT (a tiny cathrode ray tube, or TV screen) both for information projection and also for its night vision system. Night vision can be built into your vehicle either as a head-up display or as an in-dash display.
The CRT HUD is out of favor because of its bulk and power requirements. As LED arrays grow in resolution, they could conceivably reproduce most or all of your current dashboard display in the head-up display. Researchers are wrestling with the question of how much is too much: If a navigation arrow is good, does a complete map display in your line of sight represent information overload, and is there a happy medium such as a rudimentary map?
Alternatives to HUDs
For those who can't get a head-up display in their next car, you may find it preferable if the navigation system display is mounted high up on the console, easier to read at a glance. Some cars use a multi-information display (MID) in the instrument cluster that shows a navigation arrow and name of the next exit or street, or the name of the current radio station and artist. The high-end Mercedes-Benz S-Class sedan uses a glass cockpit that is a large LCD panel, reconfigurable to provide different types of information as needed. And Saab has a night mode to minimize distractions after dark: Everything goes dark except the speedometer; if something goes amiss, a warning light comes on.
Bio: Bill Howard is an experienced automotive writer and the editor of TechnoRide.com, the car technology site produced by Ziff Davis. Previously, he was PC Magazine's executive editor. Howard is also vice president of the International Motor Press Association.
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