On December 26, 1999, about 1700 mountain standard time, a Piper PA-24-250, N5933P, registered to Rocky Mountain Air, and operated by the commercial pilot, was substantially damaged during an off-airport landing 10 miles south of Jordan Valley, Oregon. The aircraft was being operated as a 14CFR91 personal/pleasure flight. The pilot, the sole occupant of the aircraft, was not injured. Marginal VFR conditions prevailed and a flight plan was on file. The flight originated from Pocatello, Idaho, approximately 4 hours prior to the accident. There was no fire and no report of ELT activation. In a written statement, the pilot reported that he departed Pocatello Regional Airport, via a special visual flight rules (VFR) clearance, with an intended destination of Boise, Idaho. While en route, the pilot noted that all the airports along the route of flight were fogged in. The pilot reported that upon approaching Mountain Home, Idaho, which was also fogged in, he intended on flying an instrument approach into Boise (due to low ceilings and fog), but realized that he had forgotten his instrument approach charts. The pilot attempted unsuccessfully to find a nearby airport that would allow him to land under VFR conditions. While attempting to find a VFR airport, both left and right main fuel tanks ran out of fuel. The pilot estimated that he had approximately five gallons in each tip tank and elected to initiate a precautionary landing on Highway 95. During the landing roll-out, the aircraft collided with a road marker, subsequently damaging the leading edge of the aircraft's wing and wing spar.