DALLAS (AP) – At a time of high tensions between police and the public, the Dallas Police Department seems to be a success story. While some other big-city departments draw thousands of citizen complaints every year, the nation’s eighth-largest gets only a fraction of that number. But a closer look suggests that the apparent success may stem from the complaint system itself. The Associated Press found that the system makes it so hard for people to complain that many do not try or give up. Those who persist confront a host of built-in obstacles, including vague or nonexistent instructions, confusion about complaint forms, incorrect phone numbers and a mysterious investigation process. Decisions often go unannounced and are difficult to appeal. The police chief plans to announce changes in the next few weeks.