While returning to the airfield the glider experienced a deterioration of lift and the pilot decided to carry out a landing on the Stuart Highway. The pilot observed two vehicles on the road and attempted to warn them of his intention to land. The first vehicle stopped but a bus following, continued along the roadway. The pilot decided to land before reaching the bus. After touchdown the pilot moved the glider to the side of the road but the left wing struck a road sign then a tree. The glider slewed off the road and the landing gear was torn off. The pilot was forced to accept a collision with known obstructions in order to avoid the bus. The countryside in the vicinity of the highway was considered unsuitable for an outlanding.