I was driving home from a business meeting taking some back roads. Saw an object that was straight in front of me, which at first looked like a bright light that I thought was a plane heading towards me at first, but as I got closer it grew in size. There was no sound and once I got closer saw it was stationary and I then realized it was not a plane or helicopter.As I got closer, I could see some lights on its underside and I passed almost directly under it as it was off to my left partially obscured by trees but very close to the tree tops in a very thickly wooded section. The lights made its structure partially visible. It appeared to be a somewhat disc shaped object although not perfectly round and appeared to be concave on the bottom, about 30' in diameter, with a few green and red lights glowing constant underneath, it also had a bright white light that I could see as I approached it and was just above treetop level. It also looked like it had some sort of I-Beam like structure across the bottom that was flush against the concave bottom with a round structure in the very center. The trees were partially obscuring it at the closest point so I didn't get an enormous amount of detail I was shocked when I realized what it was and was also upset because there was a car on my bumper that kept honking its horn at me - I must have been slowing down to look at it. I would have pulled over except for the driver on my bumper and I was also quite startled. I lost sight of it when I passed under it and kept driving. I told my wife when I got home - I was still startled and quite shaken about it, which actually surprised me.I have seen several UFO's in the distant past but nothing this close where I could make out the structure of the craft in any kind of detail. My wife and I drove back to the area which is close to our home about 15-20 minutes later with a camera and flashlight but saw nothing.