A Saab 900 plays an important role in this film. For shooting they used more than one car. There is a long scene where the protagonists are driving along the country shot from different angles in which you can see that one car does have a sunroof and the other does not. So every view seconds the "outfit" of the car changes.
At their first stop, when Alex is trying to hitchhike, you can see him wearing some kind of sandals. However, when he returns to Marie and Vincent a few seconds later, you can see him wearing some old running shoes.