If Catherine's love making in the first scene is detached, then this stands in stark contrast.  The love making here is hurried, frantic, and speaks more of lust than anything else. 

The opening shot is one we'll see throughout the movie, a view from what is apparently the inside of a vehicle, looking outward.  However, in a subtle piece of humour, we see this mock-up wheeled away.  For a moment we are inside the world of Crash, only to find it a fiction.  Ballard is making a crash promotional work, and the prop is being readied for its demise.  We learn that Ballard is a Producer, explained through a simple line of dialog:  “Has anyone seen Ballard, the Producer of this epic?” 

Ballard is in a room, having sex with a camera girl (we see her later in the movie during a brief scene when Ballard takes a call from Vaughan).  Since they are interrupted they begin to make love more urgently, the girl pulling him into her, Ballard trying to rush to orgasm.

This scene forms a triangle of love, lust, and voyeurism.  It helps us position the characters so we can better understand why they might be susceptible to what will follow.

As an interesting footnote - it is known that footage was cut from Crash.  Some of the footage cut include several sex scenes between Ballard and his secretary.  The reason given for these cuts was that the "chemistry between the two characters was too good".

As it stands then, this is the single instance of extra-marital sex Ballard will have with a character outside of the Crash circle – as it is with Catherine in the previous scene.  From here on in, there sexual energies will be focused into Crash, and the characters they are yet to meet.