Most great drama is about moral choices.

The central characters must decide between good and evil and suffer the consequences. The audience identifies with the protagonists’ dilemmas, observes the foolishness or wisdom of their positions, and leaves the theater enlightened.

Changing Lanes doesn't rise to this level. But, unlike most current Hollywood product, every twist and turn of its plot depends on the moral choices of its main characters. Director Roger Michell (Notting Hill) and screenwriters Chap Taylor and Michael Tolkin (The Player) skillfully put us through the emotional wringer. But the filmmakers pull back when the moral heat gets too intense, opting instead for some sharp social commentary and the conventions of a well-made thriller.

The action begins with the collision of two Manhattan motorists on FDR Drive, then plunges us deep into the depths of their respective bouts of road rage.

Both men are late for court appearances. Gavin Banek (Ben Affleck) is a high-priced, well-connected attorney in a large, powerful firm. He wears expensively tailored clothes, lives in the best part of town and dines out at tony restaurants. His complacent arrogance is fueled by an unearned sense of entitlement. He's both successful and cool — a perfect example of the kind of 21st-century yuppie ordinary folks love to hate. We yearn for him to get his comeuppance, and the filmmakers work hard to grant us our wish.

Banek is driving to a probate hearing at which he's to present documents that will cinch his firm's fraudulent takeover of a charitable foundation. His luxury car rams the aging vehicle of Doyle Gipson (Samuel L. Jackson), an African-American insurance agent who's on his way to a family-court hearing at which he hopes to be awarded joint custody of his children. Gipson is a recovering alcoholic whose erratic behavior drove his wife to walk out.

The two men react differently to the accident. Gipson is a working-class stiff intent on rebuilding his life. He wants to do the right thing and exchange insurance information. Banek, the upscale lawyer, is used to cutting corners and getting things his own way. He ignores Gipson's request, rushing off to court after handing the seemingly decent man a blank check.

The insurance agent's car is disabled, and he can't get a ride. This makes him late for his court appearance and costs him the custody of his kids.

Banek doesn't fare much better. In his haste to leave the accident, he's forgotten an important file. The probate judge orders him to recover it by the end of the day.

Gipson finds it after he's suffered his own setback and, once again, his instincts are the right ones. But Banek tries to pressure Gipson into conforming to his timetable, illegally altering the insurance agent's credit record and making other unethical moves.

This turns Gipson into Banek's nemesis, and the rest of the film is a contest between the two men to see who can inflict the most damage on the other. “Maybe God wanted to put two guys into a paper bag and let ’em rip,” Banek speculates.

All the action takes place during a single day, and the filmmakers choose Good Friday to put their characters to the test. They follow up with a well-meaning and appropriate exploration of the themes of sin, sacrifice and redemption.

At first our rooting interest is with Gipson. But, as the insurance agent is thrown into the cauldron, we see that he can't control his anger. Once he's provoked, his rage can inflict almost as much harm as Banek's the-end-justifies-the-means ethos.

Banek is shown to have the flickerings of a conscience, albeit one that has been smothered by his lust for status and money. He suffers fits of remorse and tries to undo some of the harm he's done. “Everything is held together by a covenant,” he declares during one of these spasms of moral clarity.

But evil proves to be a slippery slope. Each step Banek takes across the line sets up a situation where he'll be forced to do more wrong. We watch him agonize as he slides downward.

At one point, Banek, exhausted by his duel with Gipson, wanders into a Catholic Church during a Good Friday service. Looking for a quiet place to collect his thoughts, he sits down in a confessional. A priest thinks he wants to make a confession. Banek protests, stating that he's not a Catholic, and rails against life's unfairness.

The filmmakers make us see that the young lawyer badly needs some kind of moral guidance. But the only positive spiritual point of view is presented by Gipson's Alcoholic Anonymous sponsor (Bill Hurt), who offers sage advice and talks about a higher power. This is good as far as it goes, but it's not enough.

The movie intelligently emphasizes class differences more than race, and the portrait of uptown Manhattan lawyering is devastating. Banek's mentor at the firm is his father-in-law, Delano (Sydney Pollack), who functions as a silvery-tongued tempter.

The filmmakers suggest that Banek must stand up to Delano to redeem himself and, at the end, he finds a way to beat Delano at his own game. The movie assumes that it's good enough to wipe the slate clean.

This is too neat and comfortable. Banek never takes full responsibility for his actions and never undergoes the kind of soul-searching change of heart necessary to achieve forgiveness and redemption. The filmmakers are sincere in their intention to create a modern-day urban morality play. But they don't cut deep enough to cope with the issues they've put before us.

John Prizer writes from Los Angeles.