The first commercial advertisements appeared Saturday on the outside of train cars on the JR Yamanote line since the Tokyo metropolitan government lifted a ban on such advertising in October.
Fifty out of 52 Yamanote trains were adorned with ads for the Tokyo Millenario event, which will feature light shows and be held in central Tokyo from Christmas Eve.
The ads only show the name of the event and sponsoring companies because restrictions permit only 10 percent of the side of each train to be used for ads, East Japan Railway Co. said.
The cost of the ads is free this time since JR East is one of the sponsors, according to the company.
The Tokyo Tama Intercity Monorail Co. and Tokyo's New Transit Yurikamome already have ads on their trains.
But since Kawasaki city, located between Tokyo and Yokohama, still bars trains from using this type of advertising, trains on the JR Tokaido Line or Keihin-Tohoku Line are not likely to jump on board.