each picture is a different car. about 48 cars at 12fps

Agreed.

one wish is that it ended with a few empty blank (virgin) snow windows...
quibbling, but I think it would be more dramatic.... and make for nice loop.

about 2h - I went for a walk in my district. No concept, i sketched what came in my mind.
I had this idea a long time ago and this was the perfect day, the right amount of snow but warm temperature that the snow is wet on the windows and its easy to draw on it... a bit hectic cause u have only one or two days, then either the snow is gone or the cars are cleaned by their drivers.

...and then about 2 hours for positioning the pictures in afterfx.

I tried to do some more last winter. It's really hard to find the right conditions - not too much snow, no snowfall, not too cold so the camerabattery lasts longer. And most important it has to be a sunday or a day where the people don't need their cars.