Here is a mission for you on how to stop the convoy. At mission start I set a flag of 1 to True. Set a way point at the bridge for the convoy to hold and a flag of 1 to stop that condition. Put a static object landmine on the bridge. There are had to see. Make sure the landmine is on the opposite side of the road because they are live even though they are static. Bomb the bridge. When the landmine is dead set a flag of 1 to off and the convoy will hold at that way point. If you dont hit the bridge before the convoy gets there the hold action will be off.
To add there is a set of cars NW of the convoy. Save them as a template. Then you cant set the convoy to hold and that template. After the explosion they go to that template. Stop.miz