Large triangular object glided crosswise over traffic on highway, descending, banked 45 turning 90 and appeared to land.Traveling by car westbound on State Highway 17, 45MPH, 6:15 A.M., lots of other traffic both directions. Approx. 4 miles east of Exit 119 (intersects with State Highway 302 which leads to Pine Bush 10 miles away. Map says that location is Scotchtown. First saw in distance group of white lights with central blinking red light moving from my left to my right, very small, off in distance, assumed to be aircraft. Approx. 1 mile east of Exit 119 suddenly aware of very large (size of 737 at least) three large white lights substantially touching each other in horizonal row. Altitude approx. 300 ft. decending silently as though gliding, 60 MPH. Passed over 17 over traffic, continued to my right descending over trees and rooftops and then turned left toward Pine Bush, banking 45 degrees, revealing three large white moderately bright circular lights defining perfect equilateral triangle and a same size circular red light in center, none of which were blinking. Area between lights appeared black & triangular, barely distinguishable from sky which was still dark and cloudly (completely overcast). Observed through windshield while moving. Passed about 100ft. over and in front of me. Object descended far enough to disappear below my horizon (terrain to my right at that point is below elevation of 17, only treetops and rooftops of buildings are visible). I did not pull over to shoulder because of traffic risk. Within seconds saw roadsign saying "Pine Bush". Passed same but doubled back onto 17 and then 302 and a side road off 302 in direction of apparent landing looking for object but did not see it again. No airport close by.