On May 25, 1997, about 1400 mountain daylight time, a Centrair 101C glider, N991JB, was substantially damaged when it collided with a guardrail during a forced landing on a highway approximately 21 miles southeast of Santa Fe, New Mexico. The private pilot, sole occupant of the glider, was not injured. The glider was registered to and operated by the pilot under Title 14 CFR Part 91. Visual meteorological conditions prevailed and no flight plan was filed for the personal flight that originated from Moriarty, New Mexico, about 1230. In a written statement, the pilot reported that he planned a 500 km trip to Colorado. Initially, the flight encountered thermal conditions in the Moriarty area that were "extremely strong, showing thermal strength in the range from 1000 to 1500 feet per minute." However, upon reaching a point approximately 30 miles north of Moriarty, the pilot "noticed a considerable weakening of conditions" and decided to make his destination the Santa Fe County Municipal Airport in Santa Fe, New Mexico, located "about 20 miles away." The pilot "attempted several times to penetrate towards" Santa Fe, but "encountered strong sink" each time. While making these attempts, the glider was "blown east" by westerly winds. Thermal "conditions to the east looked acceptable" to the pilot, and he elected to "have the wind drift" the glider towards the Las Vegas Municipal Airport in Las Vegas, New Mexico, located "[approximately] 40 miles east." As the glider drifted east, the pilot "noticed that the average lift was gradually decreasing and the top of the lift was slowly coming down." As he "fought the deteriorating conditions," the pilot "looked for suitable land out areas." When the glider reached an altitude of 1,500 feet agl, the pilot "decided that a land-out might be inevitable" and began planning an approach to land on the southbound lanes of Interstate 25. According to the pilot, he selected the highway as the only available landing area due to numerous trees in the surrounding terrain. The glider touched down in a gap in traffic and "settled with both wings on the guardrails sliding forward." At a speed of "about 10 mph," the nose of the glider turned left, and the "fuselage slid slowly into the left guard rail." The FAA inspector who examined the glider reported that a crack midway between the canopy and the empennage extended around 3/4 of the fuselage's circumference, and the trailing edge of the left wing was delaminated.