How do I make the train go forward and take damage in Snowplow?

I recently played on the new 'Snowplow' map for TF2, and while it seems easy enough to make the train go forward for Blu team, I wasn't actually making it go forward myself - I assume my teammates were doing something while I was busy taking out sentry nests as a spy - so the map has left me a little confused.
Even more confusing to me was playing defense, where every 1 minute or so, the train would inexplicably take damage without any apparent input from my team at all.
What exactly makes the train go forward in Snowplow, and how does the train take damage?
Best Answer
In Snowplow, the objective for team A is to get the train across the map, and team B must stop them. There are three control points that must be captured to gain clearance for the train to move forward, and upon team A's capturing of the point, it will speed towards the subsequent one. Every 30 seconds that team B defends the control point, the train will take damage (a car is seen being dropped on the train to inflict damage upon it) for 10% of its maximum 100% health.
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Snowplow Train test Dec. 12, 2020, at Train Mountain
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