About 10:10 a.m. Pacific daylight time on May 30, 1986, a southbound intercity charter bus operated by Starline Sightseeing Tours, Inc. went out of control while negotiating an S-curve on U.S. Route 395, about 11 miles south of Walker, California. The two-way, two-lane, mountainous roadway was clear and dry. The bus initially crossed the center line to the left and then veered back across the roadway, onto the right shoulder. The bus then swerved left and right again, and its rear struck a rock retaining fence on the right shoulder. Continuing forward, the bus crossed into the northbound lane, overturned and slid on its left side, rolled over onto its roof, and came to rest upright in the West Walker River. As a result of the accident, 21 passengers died and 19 passengers and the driver were injured. The primary safety issue in this accident concerns commercial busdriver preemployment screening and postemployment supervision by motor carriers and oversight of the carrier by the State of California, and the Federal Highway Administration (FHWA) Office of Motor Carrier Safety (OMCS). Another safety issue was the adequacy of the systems available for the exchange of data on the driver's accident and driving violation records. The Safety Board also examined the stability of the bus in the event of deflation of an air spring (part of the suspension system).