On September 21, 2003, at 1555 central daylight time, a Cessna 182S, N775WB, piloted by a private pilot, sustained substantial damage when it overran the end of runway 12 (2,937 feet by 100 feet, asphalt) and impacted a ravine at Joliet Regional Airport (JOT), Joliet, Illinois. Visual meteorological conditions prevailed at the time of the accident. The personal flight was operating under the provisions of 14 CFR Part 91 without a flight plan. The pilot and passenger reported no injuries. The flight departed Iowa City Municipal Airport (IOW), Iowa City, Iowa, at 1215. According to the pilot's written statement, the airplane started to lose electrical power approximately 12 miles west of JOT. The pilot reported the electrical power "came back sporadically and at 9 miles west I called an emergency..., telling them where I was and that I intended to land on runway 12." The pilot stated after making the emergency call, the airplane lost all electrical power. The pilot reported that prior to landing on runway 12, he observed an airplane taxi onto the runway. The pilot stated he advanced the throttle; however, the engine did not respond. The pilot reported, "I had no other choice but to land over the plane on the runway. Flaps were not extended because of the electrical failure, therefore my touchdown was 3/4 the way down the runway." The pilot stated the airplane overran the end of the runway and traversed down a ravine. Representatives of the National Transportation Safety Board and the Federal Aviation Administration (FAA) performed an inspection of the airplane subsequent to the accident. The Safety Board investigator-in-charge (IIC) performed a normal start of the engine utilizing an auxiliary power unit. The engine started with no hesitation and ran at various power settings with no anomalies. Inspection of the electrical system revealed that the alternator had an open field, resulting in the complete discharge of the electrical system. During a conversation with the Safety Board IIC, the pilot reported he should have preformed a go-around upon seeing the aircraft taxi onto the runway.