Running creatures over with minecarts

[Lupine]

Recently, I was DMing a session where the characters were fighting orcs and hobgoblins in a mine. (the two were fighting each other too).

In one room, there was a minecart loaded with iron ore, and one of the players asked if they could run over a creature with the minecart to damage. I hadn't considered that the cart would be used for anything but cover, but I also couldn't think of a reason why not to.

My snap ruling was that a creature could use its action to speed up the cart by ten feet per round, up to their top speed, dealing 1d6 bludgeoning damage per ten feet speed if empty, or a 1d10 per ten feet speed if loaded down. I also said that a cart would slow five feet for every ten moved, if it wasn't being moved.

The party ended up retreating, and plan to return. I expect they'll try this again, and I want to allow it, but I want a firmer understanding of the rules for this kind of thing.

How would you rule this? (Please bear in mind that the party includes a 7th level wood elf monk)

[Lunali]

I think I'd let them push it up to their speed with an action, double their speed if they spent a second action and movement on it. Just d6 for empty d10 for full for damage (no increase for the speed) with pusher's athletics vs athletics/acrobatics of the target or be knocked prone, advantage on the pusher's athletics if they took two turns at it.

[Yora]

In the heat of the moment, I would probably have said that if it makes sense to get the thing to full speed, enemies on the tracks would have to make a DC 10 reflex save or get hit for 10d6 bludgeoning damage.

[ImproperJustice]

Just pushing it forward on a level plane would be slow and not that dangerous unless they were prevented from getting out of the way.

If that cart builds momentum heading down an incline then somebody’s gonna die.
The previous poster for a an all or nothing dex save vs. 10d6 bludgeoning is about right.

[JackPhoenix]

10d6 is way too much. Check Improvising Damage section in the DMG (p. 249).

I agree with OP's ruling, and consider it about perfect solution.

[Naanomi]

I could also see it knocking people prone on a failed save