Reached home, saw that the sunset might be good and just took the camera to the nearby vantage point.
K1+M28/3.5, a really handy 28mm.
The 4 frames of pixel shift means that we almost have 4 frames of continuous exposure. (very useful for light trails)
So this can be easily processed out in Raw Therapee as 4 different pixel shift shots each using a different frame as the main image.
In other words, the traffic trails captured in each frame will be different.
After this, its just a matter of layering them in photoshop and using the "lighten" blending mode to only superimpose the light trails.
As usual, here is the full sized file. (flickr compression just does not do the files justice)
IMGP8750-PS-bld-1.jpg - Google Drive