Traffic is the flux or passage of motorized vehicles, unmotorized vehicles, and pedestrians on roads; or the commercial transport and exchange of goods; or the movement of passengers or people.
In Mexico, police officer Javier Rodriguez (Del Toro) and his partner, Manolo Sanchez (Vargas), stop a drug transport and arrest the couriers. Their arrest is interrupted by General Salazar (Milian), a high-ranking Mexican official, who decides to hire Rodriguez. Salazar instructs him to locate and apprehend Francisco Flores (Collins, Jr.), a notorious hitman for the Tijuana Cartel, headed by the Obregón brothers. Meanwhile, Robert Wakefield (Douglas), a conservative Ohio judge, is appointed to head the President's Office of National Drug Control, taking on the title drug czar. Wakefield is warned by his predecessor (Brolin) and several influential politicians that the War on Drugs is unwinnable. His honors student daughter, Caroline (Christensen) has been using cocaine, and develops a drug addiction after her boyfriend Seth (Grace) introduces her to smoking (free-basing) cocaine. Caroline and Seth are arrested when a fellow student overdoses on drugs at a party and they unsuccessfully try to dump him anonymously at a nearby hospital. Robert finds out that his wife Barbara (Irving) has known about their daughter's involvement with drugs for over six months. A third story is set in San Diego, where an undercover Drug Enforcement Administration (DEA) investigation led by Montel Gordon (Cheadle) and Ray Castro (Guzmán) leads to the arrest of Eduardo Ruiz (Ferrer), a high-stakes dealer posing as a fisherman. Ruiz, who is hospitalized as the result of a gunshot wound from the arrest, decides to risk the dangerous road to immunity by giving up his boss: drug lord Carlos Ayala (Bauer), the biggest distributor for the Obregón brothers in the United States. Ayala is indicted by a tough prosecutor, hand-selected by Wakefield to send a message to the Mexican drug organizations. Under torture, Flores gives Salazar the names of several important members of the Obregón cartel, who are arrested in a large effort by police and army soldiers. Rodriguez and Salazar's efforts begin to cripple the Obregón brothers' cocaine outfit, but Rodriguez soon discovers Salazar is a pawn for the Juárez Cartel, the rival of the Obregón brothers. That entire portion of the Mexican anti-drug campaign is a fraud, as Salazar is wiping out one cartel because he has aligned with another for profit. Wakefield realizes his daughter Caroline is a drug addict and is caught between his demanding new position and difficult family life. When he heads to Mexico, he is encouraged by the successful efforts of Salazar in hurting the Obregón brothers. When he returns to Ohio, Robert learns his efforts to see Caroline rehabilitated have failed. She ran away into the city of Cincinnati, where no one knows her location. Secretly, she is prostituted to a drug dealer, and robs her parents to procure money for drugs. As the trial against Carlos Ayala begins, his pregnant wife Helena (Zeta-Jones) learns of her husband's true profession. Facing the prospect of life imprisonment for her husband and death threats against her only child, Helena decides to hire Flores to assassinate Eduardo Ruiz; she knows killing Ruiz will effectively end the trial nolle prosequi. Flores plants a car bomb on a DEA car in an assassination attempt against Ruiz. Shortly after planting the bomb, Flores is assassinated by a sniper in retaliation for his betrayal in cooperating with General Salazar; the car bomb kills Castro, but both Gordon and Ruiz survive. Rodriguez's partner, Sanchez, attempts to sell the information of Salazar's true affiliation to the DEA, but is killed for his betrayal. Rodriguez, who can no longer stomach working for Salazar, decides to cut a deal with the least corrupt organization he has access to: the federal government of the United States and the FBI. In exchange for his testimony, Javier requests electricity in his neighborhood, so the kids can play baseball at night rather than be tempted by street gangs and crime. Salazar's secrets are revealed to the public, and he is arrested and secretly tortured to death. Wakefield drags Seth along as he begins to search Cincinnati for his daughter. After being threatened and nearly killed by a drug dealer, Wakefield breaks into a seedy hotel room and finds a semi-conscious Caroline acting as a prostitute to an older man. Wakefield returns to Washington, D.C., to give his prepared speech on a "10-point plan" to combat the war on drugs. In the middle of the speech, he falters, then tells the press that the War on Drugs implies a war even on some people's own family members, which he cannot endorse. He then walks out of the press conference, quits his job, and heads home. Helena, knowing Ruiz is soon scheduled to testify, makes a deal with Juan Obregón (Bratt), lord of the drug cartel, who forgives the debt of the Ayala family and has Ruiz poisoned. Ayala is released, much to the dissatisfaction of Gordon, who is still angry over the death of his partner. Soon after the release, Gordon bursts into the Ayala residence and surreptitiously plants a microphone under one of the tables, before being kicked out. Robert and Barbara Wakefield begin to go to Narcotics Anonymous meetings with their daughter to support her and others. Rodriguez explains to the media about the widespread corruption in the police force and army. In Mexico, Rodriguez watches as children play baseball at night in their new stadium.  Relationship to factual events Some aspects of the plotline are based on actual people and events. The character General Arturo Salazar is closely modeled after Mexican General Jesús Gutiérrez Rebollo, who was secretly on the payroll of Amado Carrillo Fuentes, head of the Juarez Cartel. The character Porfilio Madrigal is modeled after Fuentes. The Obregón brothers are modeled after the Arellano Félix brothers. At one point in the film, an El Paso Intelligence Center agent tells Robert his position, official in charge of drug control, doesn't exist in Mexico. As noted in the original script, a Director of the Instituto Nacional para el Combate a las Drogas was created by the Attorney General in 1996.