I think there is a factor not thought of. The truck just came over a railroad track. Most railroad tracks are ruff and raised up some compared to the approaching road and the road leaving the track. The truck went over the track too fast and when the final axle was on the track all the weight was transferred to that span between the real tandem and the axle at the far back causing all that weight to broke its back. Another thing is it was an aluminium trailer, I would like to know just what king of experience that person had. A very good case of operator error.
Nelson