How can a steep driveway be kept safe in snowy climates?
Having lived a good portion of my life in an area where heavy snowfall is common I can say that the best way to deal with snow in any driveway is to keep it shoveled out down to the underlying surface. You should at all possibilities try to keep it shoveled, plowed or blown before any attempt to drive on it. In many cases driving on it compacts the snow down and begins to cause a build up of compacted snow ice that will tend to want to stay there for the rest of the winter. These comments can apply to any driveway but especially to one like you describe which is a serious grade.

In my last years of living in snow country I had a medium steep driveway that rose about 6 feet over a run of about 45 feet. I was working long days at my job and there were multiple drivers in the family that used the driveway multiple times before I could get it cleaned out each time it snowed. I can say that it was a mess of slippery iciness that was hard to drive in. Some years the icy build up was as much as 8 inches thick. The work around solution that I used was to spread liberal amounts of course sand over it to provide traction till the next snow.