I've seen video in the past (sorry I have not found an example), possibly on a trailer for Gran Torismo or the Akira film or something like that, where you see a rear shot of a car at night with it's rear lights on and then as it drives off the red of the rear light streaks and follows the path of the rear lights.
How could I recreate that effect with footage of car car driving off into the distance?
If I used echo or another of the time effects wouldn't that echo everything in the scene and not just the lights?
My other guess would be to use trapcode particular, but wouldn't that mean manually animating the path for the light? Maybe using the motion tracker would work?
What the best but simplest way to achieve the effect?
you could do it either way. if you used particular, then you would want to track the lights (or a part of the car). i would apply the track to a null, then parent a light named 'emitter' to the null and set the emitter in particular to 'light', which will then use that light. you may need to animate the scale of the emitter and particles over time to create depth, since your track is only on the xy plane.
if you effected the footage with echo, cc wide time or cc time blend, then you may want to use a duplicate of the footage and then mask or key (or even color adjust) the duplicate footage to have only the detail you wanted to trail. then apply the effect to create the trail. if you did a color adjust to make all other details black, then you could just set the duplicate 'trail' footage to screen or add to composite back onto the original footage.