There is an ongoing political battle in Canada about the proposed expansion of the Kinder Morgan Trans Mountain pipeline.
One argument in favour of the expansion that is repeated by just about every news article on the topic (example) is that the lack of pipeline capacity to get Canadian oil to market is causing Canadian oil to sell at a discount compared to US oil.
I'd like to understand this connection between pipeline capacity and oil price.
Naively, I would think that if pipeline capacity is scarce and the oil has to be transported by more expensive means like rail, its price would be higher to reflect the increased cost.