On January 2, 2000, at 1800 hours Pacific standard time, a Cessna 172G, N3690L, was substantially damaged during a precautionary landing on a county road at Victorville, California. The private pilot and one passenger were not injured. Visual meteorological conditions prevailed for the personal flight, which was operated under 14 CFR Part 91 by Riverside (California) Air Service. The flight departed Bullhead City, Arizona, about 1515 and no flight plan was filed. The pilot reported that 2 hours 15 minutes after takeoff, as he was flying along highway 15, the generator fail annunciator light came on. He reduced the electrical load and noted that the carburetor air temperature and exhaust gas temperature gauges were "climbing above the warning lines." The pilot contacted Southern California (SoCal) Approach Control and explained that he was "not familiar" with the area and requested a vector to the nearest airport. Before SoCal could help, the electrical power failed completely and the engine started to run rough. He decided to land on a road because he was "not sure" of his position and didn't know if the engine gauges were reading correctly. He also reported that the engine was "running rough" and "sputtering" at full throttle. As the airplane touched down, the left wing struck a street sign, which deflected the airplane across the highway median and off the other side of the road. The accident time was 2 hours 45 minutes after takeoff. According to a GTE DUATS flight plan, the low altitude airway distance from Laughlin to Riverside is 167 nautical miles, and the distance from Laughlin to Victorville is approximately 142 nautical miles. The pilot had 90 hours total flying time and received his private pilot certificate on December 9, 1999. The operator sent the engine to an engine repair facility where it was disassembled and inspected, including the carburetor and magnetos. The mechanic there told the Safety Board investigator that no discrepancies were noted that might have led to a power interruption or a rough running engine. The engine was subsequently reinstalled in the airplane and operated normally. The electrical charging system was found to be inoperative and the generator and voltage regulator were replaced.