An autorack railroad car has an underframe that, in contrast to the prior art, has a straight-through center sill that is shallower, and of diminished geometry-based sectional properties generally, in the middle portion between the trucks than at the end portions at either the draft sills at the draft gear or at the truck centers. The bottom flange of the center sill is carried at a constant height from end to end, and is free of kinks in elevation. In the mid-span portion of the car, from truck center to truck center, the center sill is shallower in section than the side sills. The bottom flange of the center sill is carried at a height that corresponds to, or is higher than, the height of the lower flanges of the side sills, such that the cross-bearer arms are shallow, and the bottom flanges of the cross-bearer arms are substantially level.