While driving southbound on i-205 south, i observed a triangular shaped, metallic silver object in motion in the air, approximately 2 miles to the south, it appeared solid and the sunlight reflected off it. the object appeared smooth, devoid of features that could be seen from a distance. its triangular shape was similar to the shape of a basic paper airplane - a slender, equilateral triangle with a base ~1/4 the length of a side. object appeared to be moving west/sw, and slightly upwards. it crossed above i-205 and continued on same trajectory, then abruptly changed direction & moved downwards and more sw, then up again. view of object was then obscured by vehicles & signs. unknown if it landed. did not sight it again.