At 1205 Mountain time, the airplane sustained substantial damage during a forced landing subsequent to a loss of engine power. The two occupants, a private pilot and a passenger, were not injured. Visual conditions prevailed; the flight originated approximately 20 minutes before the accident. The pilot later told investigators the airplane developed a rough running engine and he elected to land on a nearby road. The airplane collided with a road sign during the landing sequence, resulting in substantial damage to both wings.