Probable Cause

@kairospix: Yes, it was very considerably post processed. You can see the original image <here>

I adjusted the levels and curves individually for each of the RGB channels. Then I applied a contrast adjustment layer and blended the negative image in "grain extract" mode, which effectively erased the reflection of my truck from the back window of the van (pure luck). I think I also probably boosted the saturation a bit, which since the image was by now largely black and white only affected the tail light. Last came an application of unsharp mask.