from Sports R/A go towards Villagio road,after Villagio and Hayaat Plaza take a Left turn,that goes to Qatar Zoo,go straight you reach a new fly over go over that it will lead you staraight to industrial area,ask for vehicle inspection center and DOPET is just opposite of that.
If you take villagio road, you avoid most of the traffic and reach fast than American scholl,salwa road heavy traffic.