''In LA nobody touches you," murmurs Don Cheadle, momentarily stunned by an automobile collision that prompts a rush of blood to the head. "We're always behind metal and glass. I think we miss that touch so much that we crash into each other, just so that we can feel something." This speech, which opens the writer/director Paul Haggis's intelligent ensemble piece Crash, could easily have been lifted from David Cronenberg's much-maligned masterpiece of the same name. Despite their stark surface dissimilarities - one is an episodic social satire, the other a sleek, controversial cause celebre - both films address the fetishised substitute for emotional contact which the car crash provides in this traumatised age. Indeed, these two apparently incompatible Crash-es could perhaps be interpreted as opposite sides of the same thematic coin: parallax views of a single moving violation. Yet while Cronenberg's visceral masterpiece was informed by the pleasures of the new flesh, Haggis's film aspires (perhaps more palatably) towards the salvation of the old soul.

In the darkness of the Hollywood hills, a body is discovered at night. Amid the police traffic cones, a vehicular prang provokes a verbal scuffle that soon gives voice to the city's broiling racial tensions. As Latinos, Koreans, Caucasians and African Americans stumble from the wreckage of their personal prejudices, their pettily aired conflicts reverberate through a succession of vignettes that ripple and spiral around the crime scene. In the upmarket heart of the city, two black youths (Larenz Tate and Chris "Ludacris" Bridges) bemoan being stereotyped as thugs and muggers, before casually carjacking a 4x4. Elsewhere, a "buppie" TV director (Terrence Howard) and his wife (Thandie Newton) experience both degradation and salvation at the hands of the LAPD. Meanwhile, a high-flying black detective (Don Cheadle) weighs political expediency against personal anguish when faced with either framing a racist cop or in effect sealing his own brother's arrest warrant. Over 36 hours, these characters cross paths, impacting, overtaking or merely bypassing each other's lives in a manner reminiscent of Robert Altman's Short Cuts, Lawrence Kasdan's Grand Canyon or (most pertinently) Paul Thomas And-erson's glittering Magnolia.

Like the black comedian Chris Rock's infamous "I hate niggers" routine, Haggis's script sets out to speak the unspeakable about race relations in LA. "You liberate my country while I fly planes into your mud huts!" shouts a white gun-store owner at a customer whom he believes to be Iraqi, but who is left angrily wondering: "When did Persian become Arab?". A Latina cop advises her black lover to take a geography lesson when he casually tags her as "Mexican", only to be asked who taught so many "culturally diverse" ethnic groups to "all park their cars on their lawns". Koreans are dismissed as "stupid Chinamen", a home-loving locksmith is labelled a "Hispanic gang-banger", and, in the film's most explosive episode, the light-skinned Thandie Newton is briefly caught in the glare of a police spotlight that makes her appear white - with ter-rible consequences.

This all sounds painfully heavy-going. Yet, despite the inevitably tortuous nature of the plot, Crash is ribald, witty and frequently laugh-out-loud funny. It is also extremely moving, shot through with a down-to-earth divinity that raises each character above the level of mere cipher or stereotype. Like Haggis's script for Million Dollar Baby (which was ludicrously condemned by born-again bigots as an advert for euthanasia), Crash boasts a secular theology that comes closer to religion than many of its characters (or viewers) may wish to believe. Alongside the complex ethnic juggling, there is a quasi-Catholic sense of sin and sacrifice underlying these disparate stories, reaching a climax in what appears to be a palpable Christmas miracle. Statues of Saint Christopher, soaring choral accompaniments, guardian angels and even a cleansing fall of Yuletide snow litter this latter-day parable, underlining Haggis's quietly metaphysical intent and highlighting a spiritual dimension to the earthly ructions.

On a performance level, Crash is hard to fault, with particular plaudits going to Matt Dillon for his sterling turn as some-thing much more than just a racist cop. And credit is due to stars such as Don Cheadle and Sandra Bullock for lending their considerable box-office clout to this independently financed project. It's not perfect, and it's not Magnolia - a shortcoming most apparent in a musical montage that can only echo the magic of Anderson's electrifying "Wise Up" sequence. But after two viewings, both of which reduced me to tears, I can state with my hand on my heart that, for all its flaws, Crash is one of the year's must- see movies: a compassionate comedy of errors blessed with a profoundly human heart, but ultimately yearning for something that touches the soul.