Winter weather

The first bad winter storm is here in St Louis, we have two inches of ice and expect six to nine inches of snow by Friday morning.
What would keep your IT people from coming in to the office?
We have an 800 number to call to see if the weather is too bad to try to make it in but I question how this is done.
Is there a person who decides if it is ok to drive in to work? And how do they decide, where are they driving from and what do they use as a deciding point?
If I live in a part of the city that is not plowed or salted and the person lives blocks away will their decision make me drive in?
What are your winter weather policies?