The motor car has ravaged the Irish landscape. The edge of Dublin is a green junkyard of burnt-out, joyridden, insurance-written-off heaps. The M50 is tearing up centuries-old trees across south Dublin, while the city is a peril of ambulance chasers on mobile phones, burning through residential areas, and clocking up the "bloody slaughter" on Irish roads.

Old cars are piling up in vast scrapyards like that in Ringsend, where a petrol explosion last Saturday week caused an inferno which trailed toxic black smoke across the Dublin sky for hours. Meanwhile, joyriding remains an epidemic. Wired-up kids have a dangerous edge on the guards - once behind the wheel, they don't give a flying gazoobie.

Thirty-eight-year-old Dubliner Vinny Murphy wades into this unhappy territory with his first, flailing, full-length thriller-feature, Accelerator. It's a rough, tense, breakneck 88-minuter, with a raw vernacular Dublin humour which jack-knifes into spectacular tragedy.

In Accelerator, a gang of angry, devilmay-care kids, hang around in the moral vacuum of the housing estates and superstore car-parks of west Dublin. Faced with a nose-breaking row, they settle their differences with a bet. They decide to pair off, go to Belfast, rob a bunch of fast cars, and race back to Dublin. The deal is, they put £200 down per car, and the winner takes all.

It's a young-minded, anarchic film, full of alarming misbehaviour on the M1. But with the pace-pushing soundtrack, you happily abandon yourself to the rock'n'roll nature of the thing. Accelerator's suspense simply piles on, as the kids hurtle towards Army checkpoints and get diverted down loyalist backroads. And you can't help but squirm as the coolkid characters, Spock and Ripley, drop a tab of E and laugh their heads off at 110mph.

The whole thing was shot within a 30mile radius of Dublin by Seamus Deasy, who also shot The Boy from Mercury. And it's given a shot of adrenalin by some dark, pace-pushing drums'n'bass by Portishead's Adrian Utteley, and a bit of Brian Eno weirdness.

Accelerator has its flaws, but it's a powerful film, both frightening and affectionately hilarious, and true to the dialect and the youthful delinquency of such kids. Murphy: "But there's a great sense of morality there as well. Most criminals have a very strong and very definite sense of morality. But anybody's morality is only the morality of that group."

When I argue that morality is, potentially, a fundamental, universal principle, he counters that "in theory, yes, but things don't operate that way. There's always a group outside of that morality. Scratch the surface, and there's always a group that has the right morality and a group that has the wrong morality . . ."

Murphy worked for a decade with schoolkids in Jobstown, doing improvised theatre such as Tallaght versions of The Wizard of Oz and Hamlet, both of which he committed to video. Later, he shot three shorts with the kids on video. "I never saw it as a community project, it was just me and a bunch of people banging our heads off each other."

Three young guys in Accelerator have graduated from that group, and are now professional film actors: Jeff O'Toole, who plays Anto; Mark Dunne, who plays Crunchy, and Gavin Kelty, who plays the troubled psycho, Whacker. Murphy started working with Kelty when the latter was 10, and Kelty has landed roles in The General and the new movie about Veronica Guerin.

Accelerator cost £3 million to make, and has shown at festivals in Cannes, Montreal, Hamburg and Valenciennes - where, last weekend, it won an award for its ensemble acting, as well as a Special Jury Prize. By the time I met Murphy the following day, his head was a bit flatlined from the celebrations.

I've known Vinny Murphy on and off for years. A man of many constituencies, you'd meet him among actors, musicians, filmmakers, artists, writers or creative lefties. He started off in a punk band called the Sinners, worked with heads like Stano, did big percussion shows for, say, the Parade of Innocence for the Birmingham Six. More recently, he has brought percussion and video work into Irish prisons, even working with sex offenders. His projects with prisoners include one short video about a guy trying to kick heroin in jail.

Sadly, a good 40 per cent of our conversation was off the record. "Like every issue in prisons, it's a big problem and I don't have anything like an answer to it. There's a lot of people who work in prisons all the time, and there's all kinds of sensitivities, and I've only dipped in and out of it . . ."

I comment that there was something more profound to Accelerator than rehearsing handbrake turns and the bully-boy glamour of a head-butt in the snot. "Well, I do have an ideology, which of course comes through, but in my own head I'm just trying to make a film, and I want the performances right. Most of the cast had very little experience, and in fact one of them had never acted even in a school play."

With its pulp-thriller title, Accelerator is partly a paean to the good old-fashioned 1970s car chase. "I love films which are relentless, where you're just not let off the hook. I was thrilled at the early screenings of the rough edits. Quite a few people said `jasus, I'm exhausted after that'. Others came out feeling battered.

"Most Irish films just aren't like that. It's like we're afraid of making an exciting film. Everything seems to happen at a medium pace. Also, a lot of Irish films are either about eight-year-olds or 80-year-olds, and there's this big gap in the middle. Somewhere along the line, it's like there's a fear of dealing with what's going on around us."

Tension-wise, Accelerator eclipses comparable Irish urban thrillers like The Courier and Joyriders. "A lot of films which try to portray contemporary Dublin, it's nearly like they're set in the past. It's changing now, but just the texture of a lot of films, it's as if they're shot on old film stock or something . . ."

You have to flip your head sideways to twig some of Murphy's arguments. "And there's too much orange in Irish films. On the shoot, it became a bit of a laugh, because we wanted to take out all the reds - not for any heavy symbolism, but just to give it a look and a feel. I wanted there to be as much blue and silver as possible. I'm interested in realism in the performances, but I like the idea of things looking better in a movie than they do in real life."

Interestingly, he was relieved to get stuck back into another half-hour community video project, scripted by Mark Kilroy, for Fairview Productions: "Their idea was a community project rather than a film in its own right, but the ambition of it went up. But it was great to do that, rather than jump into another feature."

Shot in Dolphin House in Rialto, Murphy describes it as "a small story about a girl whose ma's an alcoholic, and the girl's trying to looking after the other kids, she has to get out. So she's sleeping in an unfurnished flat on a sleeping bag, and her mates decide to have a Karaoke night for her, but to get that going, they need 200 quid, so two of the guys rob it from the supermarket where they work, intending to give it back. But they do end up getting her a couch . . .

"It was amazing - we got so much help around the area. One woman, Marian, let us go into her home and shoot. She just said "ah, come in whenever you want, just tell me a few hours before. And her kid Derek had a snake, so of course I couldn't resist getting the snake into the film. She used to bring the dog around to work with her cos the dog was going mental . . ."

So, in the video, what happens to the blokes who borrowed the money off the supermarket? "They go to give it back, and one of them gets caught. So before the manager fires him, he tells him where to stuff it basically..."

Accelerator will be screened on Saturday, April 8th, at UCG 5 (the former Virgin Multiplex on Parnell Street) at 6 p.m.