Go long enough without sleep and you don't just feel tired, you feel like you're in another world. Hot and cold take turns to surge through your body as you stagger and yawn. You mumble nonsense, speak with great clarity, then relapse into mumbling again. Your eyes open and close like frustrated curtains as you drift between alertness and snoozing. The self-destructive feelings are heightened if you haven't eaten, and are surviving on cigarette smoke, or coffee, or booze. Trust me. I have experience in this area.

Frank Pierce, the New York City ambulance driver played by Nicolas Cage in "Bringing Out the Dead", lives like this for weeks on end. He sees himself as a "grief mop", paid to bear witness to hopeless situations, and it's damaging him. He gets through the long days and nights on a diet of whisky, coffee and Marlboros, begging his boss to fire him because he hasn't got the energy to quit.

The film has been written by Paul Schrader and directed by Martin Scorsese, and has been unfairly compared to their 1976 masterpiece "Taxi Driver". Both pictures feature angst-ridden insomniac protagonists who look out at the urban jungle from uncomfortable driver's seats, and both have dizzying images of garish neon light. But "Taxi Driver" was about a sensitive Vietnam vet whose terrible experiences were turning him into a psychopath; "Bringing Out the Dead" follows an essentially good man who is aware and afraid of his impending mental collapse.

Once, of course, Frank was good at his job -- acting with skill and speed, relishing the satisfaction of saving peoples' lives. Now he wanders around like a zombie, essentially performing a taxi service for corpses and crank callers. He feels tormented by the ghosts of those who he failed to save, and sometimes hears their voices: Particularly haunting is an asthmatic 18-year old girl named Rose, whose death signalled the beginning of Frank's unlucky streak.

We follow Frank around for three days, and see him work with three other ambulance men: Larry (John Goodman), a family man who dreams of starting his own private medical service; Marcus (Ving Rhames), who calls himself a Christian but has a mischievous spirit; and Tom (Tom Sizemore), who can only be described as a nutcase. Each of these men is distinctively written and played, and yet, in some odd way, all three shifts seem the same. Whoever's in the ambulance with you, it's just another miserable day on the job.

Most of the characters that are revisited by the screenplay revolve in some way around Mary (Patricia Arquette), a recovering drug addict who Frank thinks he could fall in love with. Her father is in hospital after a heart attack. A crazy guy from her neighbourhood keeps putting himself in dangerous situations, and winding up in Frank's vehicle. And her former drug dealer is given some attention, too. But none of this stuff really signifies much, because "Bringing Out the Dead" is told from Frank's point of view, and is about his inability to find meaning in anything.

That's not as bleak as it sounds, because the closing shots leave us with the impression that Frank will eventually find some peace in his life. But it is exhausting, because to get the point across Schrader and Scorsese have had to make a two-hour film in which nothing can be seen to develop after the initial set-up.

And yet I recommend "Bringing Out the Dead" as a marvellous atmospheric achievement. Like Frank, from the opening moments we're immersed in neon light and bumpy automobile movements, and in such techniques as jump cuts, dissolves, slow-motion, fast-motion and subjective camera. Scorsese's instinct to employ Robert Richardson was a good one -- the cinematographer's juxtaposition of extreme brightness and darkness create an overpoweringly drowsy mood that brings us into Frank's head. Not that it's a particularly nice place to be, as Cage demonstrates with his amazing performance -- whenever we glimpse him, he's hollow-eyed, desperate, hunched over, hesitant.

There is much dark humour in this movie, arising from the absurdity of some of the patients' predicaments, and the twisted games we see medics engage in to pass the time. But it's the harsher images that stick in our minds, because Scorsese makes us feel like we're seeing them first-hand. John Lennon once sung about "a place where nothing is real... where everything flows". I'm sure Frank Pierce would love to go there.