When rain turns to snow you can't grit because it gets washed away .
I'm with BOO - the answer is for people to drive more sensibly It's not the governments responsibility to ensure you can drive as fast as the speed limit says at all times.
I think the answer lies close to home, winter tyres if you live in an area prone to bad weather and snow chains for occasional bad weather. Add to that some common sense and things could improve considerably.