Trip in First Edition causes an object like a stick, vine, pole, etc, to become a tripwire, essentially, rising slightly off the ground and becoming 80% undetectable. Saving throw to avoid falling if you cross it, damage if you're moving too fast, bonus to save if you know it's there.
In 3E, just treat it as an Animate Rope spell with a 10 min/level duration, or something similar.
-Hyp.