Here is an interesting blog post from Critical Culture:
Although the opening of 8 1/2 is fantastic, possibly a dream had by the protagonist while stuck in his car, or a fantasy in which he manages to overcome the traffic jam, the two locations aren't mere oppositions, meant only for juxtaposed effect. Rather, they can be explained within the narrative. For, with the rise of the automobile came the rise of leisure travel and the flocking of men and women from the cities to the coast (of Italy, Spain, France, Yugoslavia)--exactly where Fellini's filmmaker hero ends up. Thus, we can assume, based on the protagonist's destination, that he, too, was on his way to the coast when the traffic boxed him in.