Three decades on, Martin Scorsese's Taxi Driver still has the power to shock, offend and exhilarate in equal measure. Donald Clarke looks back on a squalid masterpiece on the eve of its rerelease

Next week, to celebrate the 30th anniversary of the premiere of Martin Scorsese's Taxi Driver, a new 35mm print of the film will be released. It is customary on such occasions to express surprise that so much time has passed so quickly. But, really, doesn't Taxi Driver seem to have been around forever? Though Robert De Niro had already won an Oscar for The Godfather, Part II, it was Scorsese's film that solidified the actor's presence in the mind of cinemagoers. The young director, having recently shot Mean Streets with De Niro, was a promising tyro in 1976, but Taxi Driver properly secured his position as an American master.

De Niro and Scorsese have both had such unavoidably pervasive influences on modern cinema that it is somewhat unsettling to discover only three decades have passed since their second collaboration. The fetid, diseased atmosphere of the piece has - despite George Lucas's populist recapture of the citadel a year after Taxi Driver's release - seeped into the cinematic superstructure and, like a stubborn stain, proved impossible to shift. Surely the picture has been with us since the Dark Ages? A glance at the reams of prose written about it since 1976 helps reinforce this impression. Taxi Driver has managed the tricky business of being equally revered by snooty eggheads at Sight and Sound and fans of guns and disembowelling at FHM. As a result, it is close to impossible to find anything new to say about the film.

Let's try, anyway. Let's try and say 10 things rarely said about Taxi Driver.

Martin Scorsese is in it not once but twice

Everybody knows that the director turns up as one of De Niro's more sinister passengers to explain how he intends to murder his philandering wife. But who is that man with a beard lurking behind Cybill Shepherd as she enters Senator Palantine's campaign office? Why, it's Martin Scorsese. Oddly, he does not appear to be playing the same person.

The film takes place in a city going bankrupt

New York is often seen as a dangerous place in the movies, but from the late 1960s film-makers took to representing the city as a contemporary Hades. Remember the sordid streets through which Dustin Hoffman stumbles in Midnight Cowboy? Think of the dark underpasses beneath which villains lurk in The French Connection. The truth is that, by the time of Taxi Driver's release in 1976, New York City, its streets littered with potholes, was suffering a terrifying fiscal meltdown. It took close to 15 years for the books to be properly balanced. Then, in fantasies such as Sex and the City and Friends, New York came to be depicted as one big, bland department store. The city's gain was, perhaps, art's loss.

It's 'The Searchers'

Paul Schrader, the eccentric, Calvinist-raised writer of Taxi Driver, has made it clear that the structure of the Scorsese film was inspired by that of John Ford's The Searchers (1956). Both films follow a flawed anti-hero as he engages with a young girl lost to the straight world. In the western, John Wayne's Ethan Edwards seeks the Native Americans who abducted Nathalie Wood. In Taxi Driver, De Niro's Travis Bickle visits mayhem on the pimps and johns who move around Jodie Foster's teenage prostitute. On reflection, maybe "flawed" is, in respect of Travis, something of an understatement.

The end could have been even more garishly bloody

In order to avoid the awarding of an X cert, Scorsese was forced to desaturate the colours in the final shoot-out, thus rendering the bloodstains less noisomely scarlet. Schrader, pondering the suggestion that John Hinckley's attempt to assassinate President Reagan was inspired by repeated viewing of Taxi Driver, commented amusingly on such efforts to censor film-makers. "If you start banning art, what happens is that you still get Raskolnikovs," he said, referencing the protagonist of Dostoevsky's most famous novel. "You just won't have Crime and Punishment any more."

That's 'Kärlekens Språk', that is

The pornographic film to which Travis takes Betsy (Cybill Shepherd), a glamorous political campaign worker, is the hilarious Swedish cod-documentary Kärlekens Språk. The film is from that strange, forgotten genre of blue movies known at the time as "white coaters". Such flicks were so-named because, under the pretence of offering the viewer sex education, grim-faced medical professionals would often appear to talk us through the performers' erotic contortions.

De Niro in uncharacteristic faking-it shock!

Robert De Niro repeatedly flew back from Italy, where he was shooting Bernardo Bertolucci's 1900, to drive a real cab as preparation for his role in Taxi Driver. But, surprisingly, he did not actually shave his head for the final scene in which Travis sports a Mohawk haircut. The effect was, instead, created by the application of a bald wig and a strip of fur. It probably doesn't need to be said that De Niro was not flinching in his duties. The fake hair was required because the film was, as is often the case, shot out of sequence.

The picture is eerily prescient in its critiques of fame

Disturbed by the vista of Lynette Fromme, the former Charles Manson associate, who attempted to assassinate President Ford, making it onto the cover of Newsweek, Schrader conceived a denouement in which Bickle, after shooting up half of New York, would himself gain undeserved celebrity. Times have changed. In the era of Big Brother, you don't even need to buy a gun to gain renown.

The film, brutal in so many other ways, was a tad coy as regards race

In the original script, Sport, Foster's pimp, was an African-American. But, after consideration, Schrader and Scorsese decided that allowing the suggestion of a racial motivation for Bickle's eventual annihilation of Sport might be dangerously provocative. Harvey Keitel duly got the role.

That's from 'Shane' that is

It is well known that Travis Bickle's terrifying speech before his mirror was entirely improvised by De Niro. What is mentioned less often is that the monologue's most famous sequence echoes snatches of dialogue from George Steven's 1953 western Shane. "You speaking to me?" Alan Ladd says to Ben Johnson. "I don't see nobody else standing there," comes the reply."

Sorry? What?

Astral Weeks is a wistful, strummy LP by Van Morrison which trades in images of leafy suburbs and pastoral paradises. Taxi Driver is an angry, angst-ridden film set in a crumbling, violent New York. Yet Greil Marcus, the perennially elliptical American music critic, recently claimed that Scorsese told him that the first half of the film was based on Morrison's LP. Go figure.

Taxi Driver is at the Irish Film Institute, Dublin, from next Friday