The car isn't an effective private space.  It provides privacy only for those with a voyeuristic streak.  The car gives us a private soundstage, where our words are contained and held back, while at the same time opening up the walls for others to glance inside, even at high speed.  It’s an illusion of secrecy, with the sense separated out.  In the world of Crash, this isn’t a negative; it’s almost part of the celebration of new found freedoms.

Driving to the airport garage seems to simply be the nearest place where Ballard and Remington can get off the road.  However, note the opening scene of the film also takes place in an airport hangar.  Planes are eluded to several times in the movie, representing another piece of vehicular technology where you can have accidents and live dangerously. 

This first sexual encounter is by far the most adventurous and violent. In later scenes we see Ballard and Remington having sex in a car where neither of them seem much interested in having an orgasm, and they just stop, looking bored, in order to talk. 

Here however they tear at each others clothes.  Ballard is sitting in the driver’s seat, and Remington straddles him as he pulls off her panties and tights.  This shot was used, extensively, as theatrical art for the film.

Significantly it is Ballard that makes the first move, finally ready to embrace whatever is to follow.  At no point does Remington do the seducing, although she has been flirting for quite some time.  It is the clearest example yet that Ballard has come to accept these new feelings.  After all, having sex in a car with the widow of a man you killed in a head-on crash isn't exactly standard behaviours.

The sex act itself is fevered and brief, with Ballard climaxing early.  It is, after all, his first time.  Still, neither of them are disappointed.

People walk around the car, going to and from flights.  This helps us appreciate that they were not seeking out a secretive copulation, but rather, just needed to get off the road to afford opportunity, playing with the car as both a place of privacy, and one for public performance.

Finally we note the sexual position they take.  On the surface it must have been quite uncomfortable for Ballard since his leg was recently broken.  However, he remains in the driving seat, with Remington straddling him.  He is in the same car, in the same seat, with the same woman he had shared an accident with.  However, this time he is cognisant of this, and is able to pull her into the driver’s compartment with him.

In the next scene, Ballard makes love with his wife.  She has taken up the same position, only this time in their apartment.