McDonald's shows us how their "Open all night" reflective billboard works. By day, nothing. All white. Tremendously ad-free. By night it'll appear like a ghostly text enticing you to come get a coffee before you swerve off the road. It might not be the the pedestrian ghost levels of slam-on-your-breaks dangerous, but I'm pretty sure that sign would be non-kosher in Norway, where they regularly ban the H&M underwear ads for luring drivers into the ditch.
Pretty clever tho.