Metro officials seeking ways to increase revenue are hoping there's a light in the middle of the tunnel.

The transit system is considering selling advertising space inside subway tunnels, using a new technology that creates mini-movies that appear to float in the darkness outside the train windows. The technique relies on a series of illuminated panels that give the illusion of motion to a passenger on a train rushing past, much the way the images in a child's flip book appear to move.

"This is unusual, and it holds a lot of promise," said Leona Agourides, Metro's assistant general manager for communications, who will seek approval for the new type of advertising from Metro directors next month.

Selling advertising space on subway walls is one of several new ideas from Metro staff members trying to boost revenue in the face of looming deficits. Metro raised fares July 1 and trimmed costs to avert a $48 million deficit in the current fiscal year's $899.8 million operating budget. But analysts looking ahead to next year are projecting a $60 million shortfall.

So the transit agency also is considering whether to allow McDonald's Corp. to locate Redbox, its nine-foot-tall "automated convenience store" that sells everything from Q-tips to laundry detergent, in Metro parking lots in exchange for a slice of the profits. Another idea calls for allowing advertising companies to install video monitors on trains and buses to play commercials as well as "programming." All strategies require approval from Metro directors, Agourides said.

The push toward more advertising is a departure for Metro, which earns $23 million a year from advertising inside stations and on trains and buses but has historically tried to minimize commercial advertising to keep its cathedral-like stations and carpeted trains free from clutter.

"It doesn't mean we have to be a monument to brown and gray," said T. Dana Kaufmann, who represents Fairfax on the Metro board of directors. "We just have to figure out how you do advertising in a way that helps support the system without making it garish."

It is unclear how much Metro could earn from animated tunnel advertising, since the medium is new. Peter Corrigan, chief executive of Submedia Inc., one of three companies installing subway tunnel advertising around the world, said revenues depend on the location of the display and the number of passengers who would ride past. But in an optimistic research paper for the American Public Transportation Association, Submedia reported that major transit systems can earn $100 million to $200 million over five years. The company says dark, vacant subway tunnels are an untapped gold mine for advertisers and transit systems alike.

Just a few years old, animated tunnel advertising is used by two other U.S. transit systems: MARTA in Atlanta and the PATH system between New Jersey and New York City. Each of those agencies recently tested ads in a single tunnel, and both now plan to expand to other locations in their systems. Both have contracted with New York-based Submedia, the only U.S. firm in the fledgling industry.

"We're very happy with it," said Tony Griffin, manager of business development at MARTA. The transit agency has been testing ads in one location for nearly two years and has earned about $270,000 in revenue, Griffin said. The first commercial was for Dasani, the bottled water produced by Atlanta-based Coca-Cola Co., and showed a close-up stream of clear blue water pouring into a pool of blue-silver water.

"The first time I saw it, I'll never forget it," Griffin said. "I've ridden the subway many, many times before, and there's really nothing to look at outside the window. It's dark. With this, you look and see the window completely filled up with blue, moving video. You really have to see it to understand it."

Advertising experts say subway tunnel advertising is the latest innovation in the battle for the attention of the consumer. "Over the last decade, there's been movement away from traditional media -- print, TV and newspapers -- so that advertisers are looking at every possible contact point with a customer," said George E. Belch, chairman of the department of marketing at San Diego State University. "I was in an elevator in Chicago, and there was a TV screen showing ads. I go to my ATM machine, and there are ads on the screen. There's TV at the gas pump. Transit advertising has always been around because you've got crowds of people who get on a train and they're going to be there for X amount of time. But this is a more dynamic approach. It's interesting technology."

Submedia was founded in 1999 by Joshua Spodek, who came up with the idea while a graduate student in astrophysics at Columbia University. Spodek was mesmerized by the zoetrope, a 19th-century optical toy that makes images inside a revolving cylinder appear to move.

A Submedia display is mechanically simple. It has no moving parts or flashing lights. The display consists of a series of seven-inch-deep metal boxes installed side by side on a tunnel wall. The boxes are 3 feet by 4 feet and contain backlit compressed images. As the train speeds past, the passengers inside the train see images that appear to move. The train must be moving at least three miles an hour for the animation effect. Submedia's clients for the displays in the PATH and MARTA systems have been national companies, including Target Stores, Discovery Network, Calvin Klein Cosmetics, Snapple and Cadillac.

While Submedia's patented technology took three years to refine, the concept wasn't entirely new. In 1980, filmmaker Bill Brand installed 228 hand-painted panels inside the Myrtle Avenue subway station in Brooklyn. He called it the Masstransiscope, and millions of passengers saw the colorful cartoonlike images for years. But it fell into disrepair and was never restored.

In the PATH and MARTA systems, riders have reacted well to the tunnel ads, transit officials said. "We've had no complaints, and one of our customers called us up and poured on the compliments about the ad," Griffin said.

Tunnel advertising is not visual pollution, Spodek said. "Everybody overwhelmingly says it takes away from the boredom of the ride," he said. "It's not like it's taking away from a beautiful view, like a billboard as you're driving around a beautiful area in Vermont. A subway tunnel is a semi-industrial environment."