On January 2, 1996, approximately 1330 Pacific standard time, a Cessna 170B, N2761D, received substantial damage when it impacted a roadside embankment after a loss of control on takeoff approximately 15 miles southeast of Baker City, Oregon. The commercial pilot, who was the sole occupant of the aircraft and was not injured, was attempting to take off from a public highway. The loss of control followed a near collision between the airplane and a motor vehicle on the highway. The driver of the motor vehicle was also uninjured. According to the pilot, the 14 CFR 91 flight was en route from Nampa, Idaho, to Baker City. Instrument meteorological conditions existed and no flight plan had been filed. The pilot stated on his NTSB accident report that he encountered deteriorating weather conditions in the area, from which he was unable to escape, and decided to land on the highway (referred to as "Highway 30" in the Baker County sheriff's report of the accident.) He stated that the weather conditions prevented him from landing at the Baker City airport. He reported that during the attempted landing on the highway, the airplane's wingtip struck a bank on the side of the road and he lost control of the airplane. However, the sheriff's report indicated that the pilot told responding law enforcement personnel that he had landed on the highway earlier, due to the weather conditions, and was attempting to take off from the highway at the time of the accident. According to the sheriff's report, the pilot stated that during the attempted takeoff, a pickup truck rounded a corner in the road and "he then pulled up, but in his words, 'The plane wasn't ready to get airborne.'" The sheriff's report indicated that the plane then touched down several times before impacting the bank on the east side of the highway. The sheriff's report indicated that responding law enforcement personnel interviewed the driver of the pickup, who returned to the scene. The sheriff's report stated that she told them she encountered the airplane as she rounded a curve in the road. The pickup driver stated to the law enforcement personnel that she swerved to miss the airplane and that the airplane then "climbed in an upward motion." She also stated to them that "the plane came very, very close to her vehicle" and indicated to them that she had been badly frightened in the encounter. The pickup driver later verified this information in a telephone interview with the NTSB investigator-in-charge (IIC). The pickup driver stated to the NTSB IIC that she encountered the airplane head-on as she traveled east on the highway. The driver of the pickup truck furnished the name and telephone number of a local resident whose house is on the public highway approximately 2/3 to 3/4 mile west of Pleasant Valley. This local resident stated in a telephone interview with the NTSB IIC on April 18, 1996, that she saw a "little orange airplane" parked, in apparently undamaged condition, between Pleasant Valley and her house at about 0900 on the day of the accident. She stated that the airplane was parked off the side of the road, and that she had seen the airplane circling the area before she saw it parked. She stated that she asked the pilot if he was all right, and that he replied he was fine. She also said the pilot asked her details of the road such as the length of the straight stretch and where the corners were, and said the pilot told her he needed to take off into the wind. She said that later, at about 1600, she saw the damaged airplane west of its parked location. Records contained in a FAA air traffic services package assembled for the accident investigation indicated that the pilot of N2761D received two telephone weather briefings from the automated flight service station (AFSS) at Boise, Idaho on the morning of the accident, at 1503 UTC and 1606 UTC. Transcripts of both briefings indicate that the pilot gave his destination as Seattle and that he was informed both times that visual flight rules (VFR) flight was not recommended. The weather in both briefings was given as generally marginal VFR to IFR conditions along the pilot's entire route, with IFR outlook. At 2150 UTC (1350 PST, approximately 20 minutes after the accident) Baker, 12 miles northwest of the accident site, reported scattered clouds at 400 feet, an estimated broken ceiling of 900 feet, an overcast at 1,300 feet, and 7 miles visibility. On his NTSB accident report narrative, the pilot attributed his "landing" accident to improperly placing the mixture control to full rich in high density altitude conditions, stating that the aircraft's altimeter read 4,710 feet after the accident, and that the mixture setting had resulted in a loss of engine power which prevented him from being able to arrest a descent rate during his landing attempt. However, the elevation of the accident site as shown by terrain contour lines on a map in the DeLorme Oregon Atlas is approximately 3,600 feet. A post-accident photograph of the aircraft instrument panel provided by the on-scene FAA investigator showed the aircraft altimeter reading 4,100 feet. Baker, at an elevation of 3,369 feet, reported a temperature of 38 degrees F and altimeter setting of 30.09 inches Hg in its 2150 UTC surface observation. For conditions of 3,369-foot field elevation, 38 degrees F, and 30.09 inches Hg, the density altitude was calculated by the investigator to be 2,564 feet. The pilot indicated on his NTSB accident report that his last biennial flight review was in June 1993, over 2 1/2 years prior to the accident.