Word spy had among their recent entries this new term: Tunnel Advertising. At first I was confused, because I saw this Daniel Baldwin-directed mess a couple of years ago, but it turns out to be something else entirely.
T & A is actually a proposed method of endorsing that involves a long series of images emblazoned on the interior of a train tunnel to give the effect of motion images to riders. This would be Burma Shave advertising for the new millenium. ( I enjoy the bitchy comment where the host moans that no surface is safe from advertising "pestilence", as if the pristine, dark, and unseen tunnel walls are going to be missed.) Essentially it is a modern version of the zoetrope a primitive form of visual entertainment, from the days before Tivo.
The possibilities of this are intriguing in that if studios put enough money behind it they could actually show trailers inside tunnels. Water cooler talk will reignite with discourse like, "Did you see the new "Hellboy" trailer on the way in to work this morning?"