In fact, for a film built around the notion of ordinariness, Changing Lanes presented its producers with some pretty extraordinary requirements. It wasn’t just the first accident, nor even a second, far more serious car smash which could easily have taken Banek’s life: it was also a scene which required him to set off the sprinklers in his own office to create a diversion.

Since Banek’s character is a high-powered lawyer - one of the central ideas behind the screenplay is that a man at the top of his profession with a long way to fall will react just as violently as one about to bottom out - the office was a high-tech marvel with costly works of art on the walls. And since the scene required multiple takes, the whole set had to be designed with special drainage grids and quick-drying materials (the works of art were, of course, fakes, but were so good that the owners of the originals from which they were copied insisted they be destroyed when filming was complete).

In the end, though, like most great script ideas, Changing Lanes is more about moral choice than water-logged sets or traffic-clogged streets. “Life is full of arbitrary little accidents like the one that propels these guys into such troubled waters,” says Michell. “It’s not a good guy/bad guy story. It’s about standing on the brink of doing the right thing - or not.”

Gipson’s dilemma is that, as a recovering alcoholic and a divorced father, he is about to lose the right to see his children. There is only one court hearing left, and the judge is both over-worked and short-tempered. The stress of losing the last thing to which he can hold onto is beginning to tell, and the fender-bender is the thing that pushes him over the edge. As a result, what Gipson does is definitely not the right thing.

Stars Sydney Pollack as Affleck’s unscrupulous father- in-law and boss.

For Banek, on the other hand, the issue is less emotional but more complex: his boss, Delano (Sydney Pollack), who is also his father-in-law, is asking him to do something which he knows to be wrong. But, as Affleck points out, “sometimes, moral integrity gets sacrificed to keep the wheels turning”. The actor reckons his character was probably an idealistic young law student who has gradually got used to bending his ideals a little in the offices of Arnell, Delano and Strauss. His former girlfriend, Michelle (Toni Collette), is about the only honest and principled thing left in his life. And she has a pretty uphill struggle: again, Banek’s instinct is not to do the right thing.

ROAD WARRIORS Notting Hill director Roger Michell (with producer Scott Rubin and Affleck) makes his US debut with Changing Lanes.

And Pollack, an Oscar-winning director who only occasionally appears in front of the camera, agreed to take the part - not unlike Affleck and Jackson - because of the opportunity to play a character as far from his own beliefs as possible. “I’d describe Delano as a semi-cynical realist,” he says. “He’s a guy who’s ambitious, tough and unsentimental in his view of what is required to be successful in a highly-competitive world. For Delano, morality is a balance sheet. One makes up for infractions by occasionally doing good. He’s got it all worked out for himself, and that’s the kind of law firm he runs.