On June 29, 1999, at 0930 central standard time (cst), a Cessna 172, N5869R, operated by a commercial pilot collided with a sign during an off airport landing in Union, Indiana. The pilot was not injured. The airplane was substantially damaged. The 14 CFR Part 91 business flight was operating in visual meteorological conditions without a flight plan. The flight originated from Owensboro, Kentucky, at 0820 cst. The pilot was flying pipeline patrol when the accident occurred. He reported that the weather quickly deteriorated during the flight. He stated that since the airplane was not approved for instrument flight, and there were no airports nearby, he elected to make an off airport landing. The pilot landed the airplane on a road during which time the left wing contacted a 2'x 4' metal sign during the landing. This resulted in damage to both the forward and rear spars in the left wing.