Having seen this sort of topic quite a few times over the years on this, and other forums, I will answer with a question. What freight flows can be transferred to rail? Sadly the answer if very little, if any. Just about everything that goes in bulk is already transported by rail, the rest of the freight flows on the roads is usually wagon load, or shipments that are either not near a railhead, or required at a certain time.
I would like to see more freight go by rail, despite my working experience being mostly warehousing and distribution, but the reality is that a single wagon from Scunthorpe to Avonmouth (as an example) would be wildly uneconomic, even if several businesses were to join forces to send and receive goods at each end.