I might ask Dawn to join in on the answer. I'm not sure I'm an expert on the movement of oil across rail. However, what I can at least offer you, before we let Dawn take the answer, is that the more wear and tear you have on rail, the more they might need to be replaced. That's just the common-sense answer.
You can think about that even in terms of where the rail is moving, right? Railway tracks react to extreme changes in temperature or long times when it's really cold. All of those play into the wear and tear and the safety and need to be monitored and watched.
With that, I'll ask Dawn to expand more specifically on that paragraph, if she has more insight.