The BMW Z1's disappearing doors: how a 1990 car still looks futuristic

The BMW Z1, built in 1990, replaced conventional car doors with a mechanism that slides them straight down into the rocker panel instead of swinging open - leaving the entire side of the car open with no door in sight. It was a genuinely novel piece of engineering for its time, and more than three decades later, the mechanism on surviving cars still operates smoothly. The Z1 never sold in huge nu