Welcome to Prius Chat, nice of you to come looking for us to post about this. I wonder, did you try light acceleration? Some people think the way to overcome wheelspin is to floor the throttle??
Well, that's the thing with my 2004 Prius: once it senses slippery conditions, it won't even let me spin a wheel. Say that time on Bishop and Waverly, when it just decided to STOP in the middle of the intersection as I was attempting to turn left to head east on Bishop I would have expected minor wheelspin in 2-3 inches of rutted slushy snow, but not for the front wheels to refuse to turn. As I was raised to drive in winter conditions, I was taught to pretend there was an egg between the gas pedal and my foot With a Prius - at least my 2004 model - it doesn't matter if you ever so gently press the gas pedal or if you floor it. The front wheels refuse to turn, and you are "stuck" while other cars roar around you honking With my Prius, I run very aggressive studded winter tires, and that has finally turned my Prius into a good winter driver. However, once it bogs down in the snow, it just sits there. It's impossible to "rock" out as the front wheels refuse to turn, Trac light blinking at me In summer, I just avoid long steep gravel roads or driveways, as I know I'll never make it up them If you regularly drive in winter conditions, invest in a good set of winter tires, preferably studded. For gravel driveways, I always suggest test driving the car in such a situation. You may be surprised at what it can or cannot do
Did you try going really slowly? The Prius drive system makes it impossible to stall the engine. You can go less than 1 MPH if you want.
Here's an article that should be of interest. Winter Weather Warning for Prius Drivers People sliding of the side of hills is not good.
I can confirm the slippage. I was rolling through the Egg Habor Tolls on the AC xpresway and when I first noticed it. We got about 3 inches of snow down by the airport and when I stepped on the gas to accelerate once through the tolls the front wheels spun and that is when I noticed it. I thought it was a little weird, but at no time did I feel unsafe or in a situation that was life threatening.