Abstract: An over-the-highway truck or tractor vehicle having an elongate rail forming a portion of a vehicle frame and an improved battery box in the form of a unitary molded container defining multiple sides of a battery retention space. One of the sides is a base for supporting at least one battery. The container includes a moveable closure which together with the base defines the battery retention space. The enclosure allows access to a battery supported by the container for battery placement in and removal from the battery retention space. Structure including a lower step fixedly connected to the rail supports the container. Pairs of recesses are integrally molded in the base of the container. Air tanks are partially positioned in the recess in a container reinforcing relationship. Connection structure fixes the air tanks and the container together.