Freezing rain is the hard one. It slides in behind the snow along Knollwood Road, glazes everything, and can turn a cleared lot into a rink by seven. JH Contracting & Maintenance inc. plans around it: plowing early, scraping down to the surface instead of leaving a base, salting ahead of the changeover rather than after. Driveways, parking areas, walkways and steps across Greenburgh get worked on a route that repeats for as long as the storm does. The trucks go out when everything else in the valley has stopped moving, and they stay out until the first commuters find their pavement dark and dry.