Three things in my book:
-Time it takes for the flash to re-charge before you can take a picture. My camera (Sony dsc-p5) completely freezes while the flash is charging which means you can't even prepare for the next shot
-Time it takes between you pressing the button and the picture actually being taken (that will help with the cars zooming by as you said).
-Time it takes to store the picture. That largely depends on the type of storage media, and in some cases the make of it.

Good luck.