crash ending

Throughout the majority of Crash, I never really called into question the realness of Vaughan as a character. Actually I did once, but wrote it off thinking it was too "fight club-y", then remembered that Crash was actually written a long time before Fight Club. Anyway, at the end of the novel it became really unclear to me whether Vaughan is supposed to be a real character or a manifestation of some part of James Ballard's subconscious, especially during the last time they see each other before Vaughan dies when they do acid and have sex. First of all, during the "last period" of James' relationship with Vaughan, he describes Vaughan as always being subdued, depressed, and indifferent, not the way that Vaughan has acted throughout the rest of the novel. He also describes seeing signs of self mutilation on Vaughan's body. Vaughan as a character seems to be slipping away and losing his will to keep existing. Second, the way in which James describes Vaughan's body and scars is so familiar that if you didn't know better, you'd think he was describing his own body because of the level of detail that he goes into. Also, since Vaughan is a more dominant character than James, and kept a lot of people such as Seagrove, Vera, and Gabriella "under his thumb", it seems like when they had sex, it shouldn't have been James who was dominating Vaughan, but Vaughan who was dominating James. Also out of the ordinary for Vaughan's character- throughout that whole scene, there is nothing that describes Vaughan as doing anything at all, not even reacting to James fucking him. He was completely passive and submissive to James and didn't even try to have an orgasm himself at all. In fact, the way Ballard wrote it, it kind of doesn't even seem like anyone else is there. This makes more sense to me under the assumption that Vaughan is a part of James' being that he started to experience after his initial car accident. If we think back, after the accident, James first sees Vaughan in the hospital, then repeatedly after that, like Vaughan is following him, which he finds out was the case. The way James dominates Vaughan in the car feels like James' efforts to fight off the dangerous ideas and obsessions that Vaughan had implanted in his mind. After their sexual encounter and after Vaughan tries to hit James with his car, James never sees nor comes in contact with Vaughan again except for when he follows Catherine daily as she drives to and from work. He is almost like a ghost. He has a presence with them but has stopped taking direct action in their lives and controlling them. Then he dies, and at the end they seem more at ease than they did at any other point of the novel. However, what bothers me about the ending is when James narrates, "Already I knew that I was designing the elements of my own car crash". This one line makes it seem like Vaughan actually was real, and that his death is causing James to start to think more seriously about what his death will look like in the form of a crash.