A locomotive underframe CNG fuel storage system including: a crashworthy enclosure including a removable side panel and a permanent side panel welded into place; and at least one CNG cylinder module, wherein each CNG cylinder module includes a plurality of CNG cylinders stacked vertically, secured to a vertical wall, and separated by a horizontal plate, wherein the horizontal plate extends towards but does not contact the vertical wall when the vertical wall is planar and, further wherein, the horizontal plate supports the vertical wall from moving further out of plane when vertical axial weight causes the vertical wall for move out of plane towards the horizontal plate.