Union Pacific Auto rack Train With An SD70ac (only one locomotive pulled this train?!)

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I haven't seen Indiana Harbor Belt in a while. I barely made it on time for a Union Pacific autorack with an SD70ace. Just one locomotive. I've seen at least 2 pulling an auto rack.. I don't know a lot about trains. Depending on the load, and if the train has to climb a grade, it will have some locos in the front and extra power in the middle/end.
The autorack train just had one loco when I've normally seen 2/3 on the autorack,

I saw the cars lightly swaying as the train passed. idk if they are supposed to move at all.

I am a Chicagoland railfan filming the trains in Chicago
I post the videos to my YouTube channel.