It’s a wonder nobody crashed their real cars doing a double-take at a glowing Audi that seems like an apparition, appearing in a fog and then disappearing just as quickly. German ad firm Thjnk came up with this ephemeral ad campaign for the hybrid-electric Audi A7 Sportback h-tron quattro to highlight the fact that nothing but water vapor comes out of its exhaust.

“We asked ourselves, where do you place ads for the most environmentally friendly and progressive engine Audi has ever built? Nowhere. So for the car that leaves nothing behind but vaporized water, we created ads that leave nothing behind but vaporized water.”

Though the agency doesn’t specify how the effect was achieved, it seems that an LED image is projected onto water vapor to get that ghostly look. The ads were placed in busy areas of big cities at night, flashing briefly and then vanishing.

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