You are driving on packed snow. What does the handbook tell you to do with your speed?

Why

Packed snow is the middle rung of the handbook's three-step ladder, and the instruction is proportional rather than fixed: reduce your speed by half, whatever you were doing. That is a much bigger cut than the 5 to 10 mph a merely wet road calls for, and a much smaller one than ice, where the ceiling is 5 mph. Fifteen mph is a real number in the handbook, but it is a posted-style limit for blind intersections and alleys, not a weather adjustment. Two things go with the snow rule: leave more space between you and the vehicle ahead, and if you drive in snowy areas, carry the right number and type of snow chains for your tires, because chains are what give the tires traction.