You’ve heard lots about the desire to ship oil along railway tracks, but the volume estimates that demonstrate this growing trend have been spotty so far.

A recent report from RBC Dominion Securities, however, offers some more colour, noting that the volume of carloads carrying oil are up 36 per cent to date in 2012 over the year prior. Plus, six of the seven major North American carriers have seen double-digit growth.

Of these carriers, analyst Walter Spracklin noted that Canadian Pacific has seen the biggest growth, with carload volumes up 90 per cent over 2011 – though it started with a smaller base than most of its peers. The lone outlier was CSX Corp., which has barely seen its shipments of oil budge, up just 2 per cent this year.

Overall, the carriers are also benefiting from larger shipments of crushed stone, sand and gravel volumes, all of which are important inputs when drilling for oil and gas. Volumes of these materials are up 12 per cent across the sector this year.

Can the railways count on these shipments to continue skyrocketing? Maybe in the short term, but highly unlikely in the near future. Morgan Stanley analysts recently noted that an estimated rail shipment from Edmonton to a refinery New Jersey adds $20 a barrel, while shipment to Vancouver by rail would add $10.

But to get a sense of where carriers hope this trend will build to, CP has projected that outbound crude volumes could grow from 13,000 carloads, or 23,000 barrels per day, in 2011 to 70,000 carloads, or 125,000 barrels per day, in the near future.