Is this still the only way to achieve this? I'm doing a shot from above a high way and have managed to scatter cars on the road long a spline via the "path distribution" option (can we please get an option to have a random interval of the distance instead of just a fixed number?). I "solved" the distance by adding empty objects to the geometry list, but still not optimal.
I tried to animate the "distance" spinner, to get some motion blur on the cars (it's just a still image), but it's not working.
Also tried animating the scattered proxy car before adding it to the FP geo list, but this doesn't seem to work either.