Don't expect to see bare pavement during a winter storm. The primary goal of snow and ice removal is to restore traction to streets, not to create clear streets.
When temperatures fall below 15-degrees Fahrenheit, the salt melts ice and snow more slowly. The colder it is outside, the longer it takes salt to do its work, which impacts winter weather operations. During some storms, traction can be restored by moving snow away from roads with plows, and in other storms, traction can be restored by using only a salt treatment. In other cases, plowing a street may reduce traction - especially in neighborhoods.
When snow becomes tightly packed, ice forms underneath. In these instances, drivers may not plow because removing the top layer of snowpack would leave a solid sheet of ice that salt treatment cannot melt quickly or efficiently. Although it seems counterintuitive, a small amount of snowpack can increase traction and keep motorists safer than they may otherwise be.
Here's an example of what a street might look like during a normal storm versus one with ice and frigid temperatures:
In the image on the left, the street is relatively clear. This photo was taken during a snowstorm that had heavy snowfall but no ice and temperatures above 25-degrees Fahrenheit. This combination made plowing operations very effective and limited the chance for streets to refreeze. As a result, the street looked clear very quickly.
In the image on the right, the street looks relatively messy. This photo was taken during a snowstorm that had heavy snowfall, ice, and temperatures well below 15-degrees Fahrenheit. This combination made plowing dangerous, as doing so could expose layers of ice. Salt treatment was also less effective because of the low temperatures. In this situation, leaving snowpack on the street's surface was the safest way to maintain traction for motorists. Although the street looks messy, that messy look made it safer than ice-covered pavement.