Some forward-thinking media professionals are beginning to look for ways to reach millions of public transit riders with digital signage messaging.

There's a chill in the evening air; the days are getting shorter, and some of the leaves on the trees are hinting at an impending explosion of color. Fall must be upon us, and that can mean only one thing: The baseball season will soon culminate in a succession of playoff games, two pennant series and ultimately the World Series.

This year leading up to the Fall Classic, commuters entering the Times Square/Grand Central Shuttle or boarding MTA New York City Transit-branded subway cars designed to capture the feel of a baseball stadium will be immersed in TBS coverage of all four of the Major League Baseball Division Series and the American League Championship Series, or ALCS games.

A TBS press release announcing the campaign, which is crafted by CBS Outdoor, says,  "Riders will also experience video screens within the subway car, featuring up-to-date information on match-ups."

While one of the objectives of the campaign is to build interest among riders in the playoffs and ALCS games and encourage them to tune in at home, another is to take advantage of digital signage technology to reach a captive audience with advertising messaging. In the words of MTA Chairman and CEO Jay H. Walder, the Metropolitan Transportation Authority of the State of New York is "creating new, dynamic advertising opportunities utilizing the latest technology."

"Inviting advertisers to 'wrap' entire trains and the use of digital displays will generate a buzz among customers and advertisers alike," Walder said in the press release.

The TBS campaign follows an effort launched more than two years ago in the Raleigh-Durham, NC, area by Capitol Broadcasting Company and its flagship media property WRAL-TV to transmit mobile DTV signals to specially equipped busses set up to receive the signals and display news, weather, sports and other local-interest content and advertising on flat panel screens on-the-go.

It appears mobile digital signage is beginning to pique the interest of media professionals and is picking up momentum. That's quite understandable. Not only are passengers generally "trapped" in close proximity to the digital sign until the train, subway or bus comes to a halt, but also the size of the audience involved is hard to ignore.

According to one account of New York City subway and bus traffic, 7.7 million people use the vehicles daily throughout the city's five boroughs. Nationwide, the number of trips taken on public transportation is mind-blowing. According to the American Public Transportation Association, more than 2.5 billion trips were taken on U.S. public transportation in the second quarter of 2010.

With such a massive audience and technological developments that are making it easier to refresh digital signage content on-the-go as needed, expect to see more demonstrations of mobile digital signage. While it's likely to be a long time before every city bus, subway car and commuter train is equipped with digital signage technology, TBS' promotion of postseason baseball and WRAL-TV's mobile DTV transmission to digital signs on city busses demonstrate that forward-thinking media professionals view digital signage on-the-go as an up-and-coming medium worthy of serious interest.