I wonder if there's some restrictions on it's travels? I mean if it sticks over the sides of the flats, it maybe restricted on mainline travel?? (side clearance?).
Anything, not just tanks (sheet steel being very common) sticking out past the side of the car would rate a Hi/Wide restriction. Of course, the wider the load, the more restrictive the orders would be. The crew handling the restricted car would get an order listing of all mileposts and speed to run where clearances on stationary objects such as rock outcrops, buildings or cars in a siding could be a problem. There would also be noted the max. speed when passing another train and if there is a need for either train to be stopped while they pass. Opposing trains could also get an order restricting their meeting of the Hi/Wide movement.