The use of tank cars in large numbers to transport crude to the NE for refining was essentially a stop-gap wartime measure. It was relatively less expensive, and a lot faster to build large numbers of tank cars, pending completion of the major pipelines (remember the "big inch', and "little inch"?). Once these, and others were in place in '43 or so the big tank train movements were much reduced. Probably numerous smaller moves to meet demand reflections, though.
