Its not always about speed, This winter I was on interstate 93 in a 4WD with winter tyres. I was doing 25-35mph because the roads weren't treated. I still spun out, like many others. The road was an ice rink.
Humans and Control System Models need feedback to operate, and worse still... when any input into the vehicle's controls produce zero results, you will spin out.
My concern with a model in these conditions is that it wouldn't recoginize the fact that other cars were in the ditch and that it should probably slow down
When it comes to controlling the wheels to prevent sliding and slipping, the AV control system is unbeatable. The ABS and traction control on a regular car has to cope with whatever control inputs the driver has made; on an AV, the computer models the grip limits of the wheel and plans a trajectory to not exceed them. It's not just for snow but also for changing pavement surfaces and the rain.
The main limitation is still sensors in the snow, but it seems to not be that big of a deal to build sensor packages that are better at seeing in the snow than a human is.
This is the "works in a textbook" take.
Being able to plot a series of inputs that can more efficiently use available traction than a human doesn't prevent you from blundering your way into a dumb situation where the laws of physics dictate that the only possible outcomes are various flavors of bad ones.
It's not clear how often the software will chose poorly and need to brute force its way out with traction/handling. The fact that they seem to be hedging against this by putting the hardware on particularly performant cars indicates it must happen enough to matter or be rare but bad enough to matter when it does happen.
Waymo will probably also rack up a ton of technically not at fault accidents by being obtuse in traffic since there's when there's snow there's a lot less margin for the "two people trying to pass each other in a hallway" type missteps that behavior tends to create.
I don’t buy it. Proof you had actual snow rated tires on and still spun out? Otherwise I claim lies are afoot