In modern day LA some bright city planner came up with the idea for a mass transit subway system in downtown LA. If you build it, they will come.......
Inevitably, an earthquake shakes the Los Angeles area, and hapless victims are trapped inside the subway tunnel. Ted McGinley is the transit maintenance scheduler - conveniently trapped as well, so that he can come to the rescue.
Sub plots include a dirty deputy mayor who wants the folks in the tunnel to stay put so they don't find the chemical waste he's been hiding down there while pocketing the disposal fees. Roy Scheider is the head of the transit authority, and deserves better. He makes the most of what he has to work with.
Mix equal parts of the Poseidon Adventure and Daylight, mix in some really bad dialogue and acting = Daybreak.