Triangular craft hovering over bridge then moving downriver.In 1994 I was coming home from my job as a registered nurse. I was driving on Idaho highway #3/12 near what is known as the Arrow Junction. I noticed lights about 1/2 mile ahead of me that appeared to be stationary and located on the side of the river valley. The night was very overcast with no stars or moonlight visible. I thought for a moment that someone must have installed new lighting on the outside of their house because there are many new homes in that area. As I approached the bridge, however, I saw that the lights were moving down the river towards me. The lights turned into a triangular shaped aircraft that was probably about 150-200 feet above the river's surface. It was moving very slowly downriver, over the center of the water. I assume that the craft was triangular because the lights that were shining down were in a triangular pattern like this: 0 <--"front" of craft Lights---> 0 0 0 0 0 <--rotating beacons between these lights I think that there were only 5 lights on the craft, but I don't remember for sure. There were two rotating beacons in between the last three lights. This struck me as odd because most aircraft marker lights that I'm aware of nowdays are strobe-type lights. Another odd thing was that this really large aircraft seemed to be proceeding at a terribly slow rate of speed. It seems to me that it must have had to have been a helicopter because the forward speed was so slow. The lights were all white, even the rotating lights. Since the sky was overcast and totally dark, I couldn't make out the actual form of the craft. I always said that if I ever saw a "UFO" I would stop, get out, and watch it. But this was so different than anything I've ever seen before that I could not bring myself to stop and get out of my rig. I do not have an estimate of the physical size of the craft although it was very big. I used to be a paratrooper and was in Viet Nam so I am familiar with a lot of the military's aircraft and I can say that I haven't a clue as to what this thing was, other than it was big and slow. The second witness referred to above was another nurse who was driving her car ahead of mine. The Arrow Bridge is at the intersection that we both took to get home and when I talked to her the next evening at work she said she saw the aircraft and that it appeared to be hovering directly over the bridge when she turned to get on the highway that would take her home. This correlates with what I saw because I could see her car ahead of mine, turning on the bridge about 1/2-3/4 mile ahead of me and the lights at that time were directly over the bridge and appeared to be stationary. She had no other information to add about what the thing looked like. The aircraft passed by me and I continued to the bridge, then made the same turn that the other nurse made and continued home. Additional: The lights had the same brilliance and color of airplane landing lights. I don't remember any other unusual factors about the lights other than that they were very white and very bright.