It's late, I'm sleepy, and I may be missing something here. But right at this moment, it seems to me that if velocity and acceleration have the SAME sign, then the object is speeding up. And if the signs are different, then the object is slowing down.
I think there's a formula that says something like v(t) = v₀ + (a·t) .
If I'm remembering that formula accurately, then it says exactly what I tried to say in my first paragraph.
