Caltrops, Ball Bearings, and Half Speed

[elyktsorb]

So for both Caltrops and Ball Bearings, if a character moves at half speed, they can ignore these obstacles entirely.

So I'm wondering if stuff that makes a character move slower impacts this. Like, say if you Ray of Frost someone, and their speed is reduced by 10ft, does this mean they have to only move 5ft slower (assuming they have a normal 30ft movement speed) or do they have to move half of 20ft, aka 10ft.

2nd question, do the effects of Caltrops stack? Since it states that when they take damage from Caltrops, their movement speed is reduced by 10ft until they regain at least 1HP. Assuming they fail the save again on Caltrops, is it reduced another 10ft?

[OldTrees1]

I would rule that:

Caltrops and Ball Bearings require caution when moving through them. You need to voluntarily halve whatever speed you currently have rather that run at as fast as you can. If slow has reduced your speed to 15ft, then moving 15ft is you running at full speed.

The ongoing effect of Caltrops, like other effects, does not stack with itself. They already have several caltrops lodged in their foot. They sudden shock of another caltrop would still halt movement, but it does not make walking any more painful than the first batch of caltrops.