Two separate weekend rail terror scares have city officials on edge

Two terrifying rail security breaches occurred within hours of each other in the city yesterday -- including one at the World Trade Center, where a man slipped into the PATH tunnel and walked all the way to Jersey before saying he had left a bomb in the tunnel. That scare -- and an unrelated escapade involving four "urban explorers" infiltrating the under-construction Second Avenue Subway tunnel -- come just days after the feds warned that al Qaeda could be targeting US trains.