Problem: Showing light on Matte/Shadow object

[ciscocd1]

I'm working on a car crash animation in 3D Studio Max 8/ Mental Ray:

 

* I'm using a nighttime spherical panorama of the crash scene as the background (self illumination at 75%) for the animation.

* I have the 3D terrain of the scene from a digital survey which I've applied a matte/shadow material and the car casts shadows on the "road".

* The 3D camera is locked down and can pan the environment. (following the car down the road)

* It looks beautiful- lighting , shadows, glow/glare on the cars lights (thanks Jeff Patton for the glow tutorial). I have spotlights attached to the front of the car for headlights.

 

How do I show the headlights illuminating the matte/shadow "road"? Is there a workaround with a render pass? I am stuck!

 

Any suggestion would be appreciated.