There are two solutions that immediately come to mind. Is this always in the same spot or area? If so, both solutions involve placing a trigger that covers the area in question. Just be careful with the size of the trigger detection area and what type of units can activate it. If it is along a median I would imagine you would want a long but very thin rectangle that runs parralel to median. Also make sure that only AI can activate it. Also remember that triggers only checks conditions about every .5 secs I think. If you can work through that, then you could do one of the following:
1) Set the trigger condition so it activates when the AI is in the detection area that forces them to do the step over animation. I do not know the name animation (you could try to find it via
Clayman's Animation Viewer) however it is also possible that it won't work...it may depend on distance and motion.
or
2) When in the trigger you can "cheat" a little and setPos the AI just enough to get them past the median curb. Maybe not fair if they are taking fire but you'll have to weigh those risks. Good luck!