A platform assembly is supported by the main frame and includes i) a framework, ii) an upper platform foot support secured to the framework and positioned adjacent to the doorway, and iii) a first stair member secured to the framework and spaced apart from the upper platform foot support. A stair assembly is movably attached to the framework and includes a second stair member. The door is movable between i) a first position in which the door is positioned to cover the door opening so as to block entry into the cab through the door opening, and ii) a second position in which the door is spaced apart from the door opening so as to enable entry into the cab through the door opening. The upper platform foot support, first stair member, and second stair member define a stairway leading to and from the door opening. A first plane intersects the upper platform foot support, the first stair, and the second stair. The first plane further intersects the door when the door is positioned in the second position. The first plane is spaced apart from the door when the door is positioned in the first position. The central longitudinal axis lies in a second plane. The first plane intersects the second plane to define an acute angle.