A woman inexplicably stumbled onto the subway tracks at the Fifth Avenue and 59th Street N station yesterday, and an oncoming train halted a mere 70 feet before hitting her. Motorman Francis Lusk spotted the woman after the unidentified thirtysomething reportedly "walked right off the platform," and was then "incapable of moving from the track." Eep! In those few frantic minutes, heroic folks on the platform began "waving their hands frantically" to alert the conductor. But not one guy, apparently, since he was taking pictures of this terrifying thing, which ran on the cover of the Daily News this morning. In any case, Francis Lusk: today's New York hero!