Three lawsuits seeking damages totaling $52.5 million have been filed on behalf of 18 people who were traveling to Las Vegas on a chartered bus March 29 when it collided with a tractor trailer on Interstate 15 near the California-Nevada border. The bus driver was knocked unconscious and two passengers, Frank Boris, 45, of Carson and Pete Benitez, 50, of Huntington Beach tried to control the vehicle and were killed when they were thrown through the windshield, said California Highway Patrolman Richard Hostetler. A lawsuit was filed on behalf of Benitez's family in Orange County Superior Court and another on behalf of Boris' family in Los Angeles Superior Court--each for $7.5 million in actual damages and $10 million in punitive damages. The third suit totaling $17.5 million was filed in Los Angeles Superior Court on behalf of 16 other passengers--almost all of whom were injured. Named as defendants were the operator of the charter, American First Tours of Inglewood; Terry Marks, driver of the tractor-trailer; Unocal and the L. J. Miller Co., according to attorney Rod Shepherd, who represents the plaintiffs.