A head-up display (HUD) projects information — speed, navigation arrows, speed limits and warnings — onto the windshield or a small glass panel, so the driver can see it without looking down. HUDs began in military aircraft, first appeared in a production car in 1988 on a special-edition Oldsmobile Cutlass Supreme, and are now common on luxury cars. The latest augmented-reality (AR) HUDs, like the one in the Mercedes-Benz S-Class, appear to place direction arrows directly on the road ahead.

At a glance
Origin Military aviation
First car HUD 1988 Oldsmobile Cutlass Supreme (Indy 500 pace car edition)
Common today Luxury and many mainstream cars
Latest Augmented-reality HUDs with virtual images projected far ahead

How it works

A projector in the dashboard shines an image onto the windshield, which acts as a partial mirror. Special windshields with a wedge-shaped interlayer prevent a double image. The image appears to float a few yards ahead of the car, so the driver’s eyes don’t need to refocus much.

Why it’s safer

Looking down at an instrument panel takes the driver’s eyes off the road for a moment. A HUD keeps key information in the line of sight, reducing glance time.

Augmented reality

AR HUDs project a much larger virtual image that appears to be many yards ahead, allowing arrows to align with the actual lane or turn. They require precise mapping, cameras and processing. Read the W223 S-Class.

Limitations

Polarized sunglasses can make some HUDs hard to see, and too much information can be distracting. Good systems keep it minimal.

Displays for passengers

While HUDs are for drivers, rear passengers increasingly get their own displays: seat-back screens, rear tablets and, in the BMW i7, a 31-inch Theatre Screen. Read the BMW i7.