My advice: once you get past the fascination of "hey, long exposures of car lights look cool"...move to interesting shapes. You basically have two lines with two colors (headlights and tail lights). Beyond the initial "long exposures are cool" element, there needs to be more here. Maybe a message about urban life. Or speed and life passing us by. Or busy roads. Or stop and go. Lots of possible messages with this concept but you'd need to find a setting that would help you convey this. Right now, it's just two lines of light. Find a piece of the road with a nice curve to it, maybe even an "S" curve and shoot that. Or a dip in the road (so the lights disappear and then re-emerge in another part of the screen as the road rises). Or some other urban stationary lights. Or pose a stationary spectator near the side of the road. I view this as a start that you're going to then move on to a more interesting compositional element.