A combination storage and tread unit has a housing which is installed beneath a second row of seating in an automotive vehicle body. The housing has a tread pad at each end which a person can step on to reach a third row of seating when a seat in the second row is tumbled forwardly. The housing has two module-receiving compartments for storing electrical control modules and related wiring. The compartments are covered and protected by the second row of seating when the seats in the second row are in a normal occupant-supporting position, but are readily accessible when the seats are tumbled forwardly, so that the modules may be removed and serviced without removing the seats.