Two sisters were killed when their vehicles collided head-on on a rural highway as they traveled to visit each other, the authorities said. Sheila Wentworth, 45, and her sister, Doris Jean Hall, 51, were killed, along with Ms. Hall's husband, Billy Joe Hall Jr., 45. The accident occurred on Sunday about 35 miles south of Birmingham. The two often visited each other on Sundays, family members said.