Device for carrying mobile advertising images in subways
Therefore: it is considered as if it projects a series of images with a bright optical device mounted on a moving body, those images accompany the body to the velocity of same body (vehicle).
Train moving in a tunnel can carry a projection device, like projectors in cinemas, but smaller at and much lower cost. It will be mounted on the side of the train to direct the flow of light through the tunnel wall. The projector can output video (like a movie) or still images (like a slide projector). A second option could be considered more financially advantageous and easier to put into practice. We can imagine a picture that will follow the same speed the passenger or train car travels they can look like an ad displayed on a fixed panel.