A recent incident has raised the question: Why do people take chances at train crossings when one false move, one slip or one miscalculation can prove deadly? Police, safety experts, veteran railroaders and psychologists say hastiness on the part of stressed-out commuters is the main reason. Temple University psychologist Frank Farley, who studies risk-taking behavior, believes people's personalities fall somewhere between those who are completely risk-averse and those he calls "Type T" personalities, or thrill-seekers."Intelligence doesn't seem to be one of the factors," Farley said. "We say, 'God, that's stupid.' But you still get intelligent people doing it."