How is Troy’s conflict at the sanitation department resolved ?

Segregation and discrimination are an intrinsic part of Troy's life. The Sanitation Department, where he works, is no exception. All the garbage truck drivers are white whereas African American employees have to make do with relatively menial jobs, such as emptying trash cans into the back of the garbage trucks. Troy's profoundly unhappy with this unfair treatment and confronts his boss about the discrimination he's encountered. As a consequence, he's promoted to the much better job of truck driver, despite the fact that, unbeknownst to his boss, he doesn't actually have a driver's license.
Although Troy claims that he wants everyone to have the chance to drive a truck, irrespective of their color, his desire for promotion is entirely selfish. He's deeply unsatisfied with every aspect of his life, and so being given the opportunity to drive a garbage truck is a rare chance for him to feel like he's achieved something in life.