Can anyone explain why I see hoppers (grain, covered and open) before and after tankers in tanker trains?

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Can anyone explain why I see hoppers (grain, covered and open) before …

Can anyone explain why I see hoppers (grain, covered and open) before and after tankers in tanker trains?

I've seen a lot of these and would like to know the purpose.

submitted by /u/Trainfan_4862 to r/trains
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