well you can track lights and use a particular emitter that looks like a flowing light…rotoscope the cars out and set them to layer emitters with the same settings…put the same flow on their lights…depends on how “flowy” you want it….come to think of it if you track it to a motion path and set it to a mask the vegas effect might no work so bad if you shorten the length of the actual vegas stroke.
I’m a photographer too so I would suggest overall re-shooting it, slow down your shutterspeed for some nice blurrs — if you have a digital camera and the proper software you can do timelapse image sequences right to a laptop.
those were just some thoughts off the top of my head…and lots of points of elipsis
post it when your finished…I’d like to see it
Nicholas Toth
Freelance Animator
nicholastoth.com