While many anticipate the appearance of ghosts and ghouls over Halloween, police and railway authorities in Tokyo have something more frightening to worry about: naked, drunken revelers.

Extra police and security guards will be posted Friday at nearly 30 train stations, mainly on the Yamanote Line, in an effort to prevent a repeat of wild and sometimes shocking parties that took place on commuter trains in Tokyo last Halloween, police and East Japan Railway Co. said.

Police have been tipped off that a big party has been planned for Friday night at JR Shinjuku Station.

Signs have been posted at stations warning that JR East will not tolerate any hijinks.

"Warning: Any actions that interfere with or endanger the safety of other passengers, including holding parties, in stations or on trains, and all forms of violence are strictly prohibited. Violations will be punished," the signs say in Japanese and English.

The steps reflect the lessons learned last year, when inebriated pranksters — many of them Westerners — vandalized trains, exposed themselves, caused delays and triggered complaints from other riders.