The length of the LACMTA Metro Rail train varies throughout the film, starting out as a six-car train at the boarding platform, then changing from six to four and even two-car trains in different stock shots.
Throughout the attempt to brake the train, even after the "grid" is down various sections of the interior lighting are alternately either off or on at various times, which would be impossible if the grid were actually down.
Nolan Wood as well as the train dispatcher refer to the subway 'driver' as "engineer" when in fact he is either a "motorman" or "train operator." Engineers run railroad trains.
The train dispatcher is afraid that engaging the mechanical emergency brake would generate enough heat to set off explosive gases. In fact, the course of action he selects has a much greater chance of triggering an explosion by [1] sparks routinely generated by the subway's third rail power shoe, [2] the dynamic brake system he proposes to use turns kinetic energy into heat through banks of resistors, and [3] directing Nolan Wood to make an impromptu shunt is sure to create sparks.