Triangle craft with 3 solid red lights (2 in front, 1 in rear) and 1 solid white light (center), moving low and slowly along freeway.We were traveling Northbound on Hwy 51, about 1 mile south of the Hwy 51 Truck Stop, in Merrill, WI. I was driving, looked out of my drivers side window, but towards the front of the vehicle. The craft was about 1 mile away, traveling at a very low speed and a very low altitude, southbound towards our car, parallel to the freeway. The craft had 2 red lights in front of it, and a red light in the rear, center of the two front lights. After the craft passed the car, the 2 front red lights dissapeared, and a 4th light, this one white, was in the center of the craft, but was only visible from the side and rear of the craft. 3 of us were in the car, and we all saw this craft. There were no sudden movements of the craft, no sound coming from the craft, and none of the lights were flashing, meaning it was not an airplane or helecopter. The craft moved very slowly and smoothly. We followed the hwy around a curve, then lost track of it. There were also 3-4 ve! hicles around us that slowed when we first saw the craft, leaving me to assume they noticed it also.