From the trailer and TV ads, one would assume “Changing Lanes” is another mindless tale of escalating aggression. Tightly edited scenes imply a rich smug guy (Ben Affleck) leaves a righteous black man (Samuel L. Jackson) stranded after a traffic accident, then the two battle it out for 90 minutes.

Fortunately, that slick commercial isn’t fully representative of the men, their actions or this thought-provoking story. “Changing Lanes” deals with some real, complex moral issues. It sticks with its characters and doesn’t exploit them in order to orchestrate some grandiose revenge scenario befitting a C-grade thriller. In that respect, this ambitious movie has more in common with “Crimes and Misdemeanors” than “High Crimes.”

“Sometimes God likes to put two guys in a paper bag and let them rip,” theorizes Gavin Banek (Affleck), a cagey attorney who has made full partner at his father-in-law’s Wall Street company. His morning begins en route to a major court case concerning whether his firm has the documents that prove a deceased industrialist left it in charge of a multimillion-dollar charity.

On the same New York City freeway, insurance salesman Doyle Gipson (Jackson) also is headed to court, caught in a custody dispute over the right to see his two sons. His estranged wife is planning on taking them to Oregon, and he must convince the judge that he has curbed his alcoholism (and temper) enough to provide a decent home.

A fender-bender forces the men to stop at a median. Doyle wants to exchange insurance information, but, pressed for time, Gavin writes him a blank check instead. Gavin’s car is still drivable, and he heads off to the courthouse stranding the other man.

“Better luck next time,” Gavin yells  words that will come back to haunt him. Along with the check, he also leaves behind the crucial legal document that verifies power of attorney.

What follows is an increasingly potent character study that reveals two flawed individuals struggling to regain their ethical backbone. Within this road rage-fueled day (the whole movie takes place in less than 24 hours), the competing men must face decisions that will affect the rest of their lives.

The screenplay by first-timer Chap Taylor and veteran Michael Tolkin (“The Player”) finds the right balance of quiet and loud moments. Affleck and Jackson are handed some lengthy monologues  the elder actor particularly shines during a scene where he discusses his idea for a Tiger Woods commercial at a bar with two yuppie ad men. But for the most part, the stars’ performances are restrained.

The writers wisely understand that if the audience has invested enough in the characters then even subtle reactions carry great meaning. That the film’s riveting climax takes place during a conversation at a restaurant instead of a gunfight at an abandoned warehouse is proof enough.

Along with veteran actors William Hurt (as Doyle’s AA sponsor) and Sydney Pollack (Gavin’s ruthless father-in-law), the two performances that really leap out are those delivered by the men’s spouses. Gavin’s wife (Amanda Peet) gives a stand-by-your-man speech that adds new depth to the warped complexities of their relationship. And as Doyle’s wife, actress Kim Staunton brings to the surface the emotional challenges of loving a man whose “life is in constant chaos.”

Critics always remark how underwritten female roles are in Hollywood films. These aren’t.

Visually, British director Roger Michell (“Notting Hill”) employs a variety of camera techniques  alternating fast and slow motion, shots peering up through street grates, shadows obscuring only the faces of actors  that give an art-house veneer to the proceedings. His one consistent fault is that he overdoes the jittery hand-held shots, which are pervasive enough to make the picture look like an urban version of “The Blair Witch Project.”

More often than not, a movie with this many themes falls apart in its finale by attempting to make too strong a statement or by conveniently wrapping things up in sitcom fashion. (Michell’s own “Notting Hill” was extra-guilty of the latter.) “Changing Lanes” brings it all together in a redemptive (but not mawkish) manner, as the two men ultimately benefit from tough, uncompromising decisions. Sometimes the very worst days have a way of bringing out the best in people.