A hopper car discharge outflow is controlled by closure members, at least one of which is movable. The doors are hingeless, being mounted on four bar linkages, such that the distal edge of the doors sweeps predominantly horizontally while the proximal edge of the door moves predominantly upwardly. The doors move through noncircular arcs, such that the size of the vertically projected door opening is abnormally large compared to the clearance heights of the door. The doors are driven by a longitudinal shaft that is mounted within the center sill. It drives a set of single input, double output bell cranks that drive adjacent pairs of doors, and that employs an over-center toggle to hold the doors in the closed position when the car is laded. The actuators may be mounted in shelters midway along the car, and may be offset from the centersill. The actuators may be mounted predominantly vertically such that gravity may obviate the need for a secondary lock. The doors of a transverse car need not all be of the same size. The over center may include a manual release having a fulcrum with a progressive decrease in mechanical advantage.