A patent for the Apple Car describes “systems with synchronized windows” to give drivers a sort of private lighting capability.
Apple Car Windows
These windows could incorporate liquid crystal with polarizers so that drivers could adjust the amount of light that the windows let in.
Modulation of the transparency of the window may be synchronized with modulated light output from a light source. The light source may be located inside the vehicle or may be located outside of the vehicle. By synchronizing the modulation of the transparency of the window with the light source output, privacy may be enhanced or glare may be reduced.
It gets better. The car could turn this window layer on and off very fast, so fast that people inside the vehicle would see the window as fully transparent. It could time the light to turn on and off at the same time as the window layer, so you could have lights on inside the vehicle but people outside the car wouldn’t see the light.