I’d like to make a general comment following your comments on compulsory ESP installation. I have driven many miles on snow in Scandinavia over 20 years and the worst incident I have encountered was I'm pretty sure a direct result of what you describe. My rented A6 yo-yo’d back and forth across the lane until the speed reduced to the point where I regained control - very frightening indeed. We would call this Pilot Induced Oscillation in my business, where the pilot reaction and aircraft response are out of phase and cause the oscillation to get worse rather than better.

I write just to say that the reason that this seemed to occur was that I was driving down two strips of tarmac on an otherwise snow-covered road. Thus the coefficient of friction varied as I traversed it and (possibly as a result - I'm not sure) the ESP gain (countering response) seemed too high and overcompensated. Given that many snowy roads develop these tracks I am very surprised that we have not heard more of this phenomenon. Something perhaps for you to monitor.