With winter conditions rapidly approaching, snow and ice control on our streets and highways becomes a priority for highway crews. Decades ago, roads were seldom plowed until morning and almost never sanded or salted. Today, however, with our very mobile society, we expect bare roads throughout the winter. Proper control of ice and snow has become very sophisticated and, indeed, more scientific.

However, we should acknowledge that it is not possible to provide a “bare” or “wet” pavement surface all of the time. The characteristics of weather events and finite available resources preclude this possibility. The interactive effects of pavement temperature, air temperature, storm intensity and timing of initial treatment, operational cycle time, traffic volume, wind velocity and solar energy all have a profound influence on the effectiveness of snow and ice control measures.

The state Department of Transportation’s goal is to provide highways that are passable and reasonably safe for vehicular traffic as much of the time as possible within the limitations imposed by weather conditions and the availability of equipment, material and personnel. Due to resource limitations and weather conditions, pavement surfaces will be snow covered and/or slippery some of the time. The goal of county, town and village DPWs, whether stated or not, would likely be similar. The traveling public must exercise caution and drive appropriately in those situations.

The challenge is how best to accomplish this goal. This includes the decision to use sand versus salt and how much. Many citizens, not familiar with the scientific rationale for this decision, prefer the use of sand. They generally believe that sand is better for the environment and is less costly than salt. However, this is not necessarily the case.

Many things need to be considered for prudent snow and ice control. Some of these include, in no particular order:

¯ Traffic volumes — higher volumes result in mixing action along with heat from tire friction. They are also an indication of “more important” roads.

¯ Day of the week — different traffic patterns.

¯ Corridors — certain roads are key to functioning of the system.

¯ Geometrics — steep grades, curves, bridge decks, etc. all influence application rates.

¯ Cold spots — areas of higher elevation or shaded areas normally require more salt.

¯ Plow speed — varies considerably due to traffic. High speed roads versus slower speeds.

¯ Time of season — more chemicals are required in January than in March because of colder pavement temperatures and continued cold weather.

¯ Sunlight — amount and angle of sunlight influences pavement temperatures.

¯ Type of snow or ice.

¯ Intensity of precipitation — the harder the snowfall the more chemicals are needed to prevent bonding. It’s much easier to clear roads from snow and ice if it hasn’t bonded to the pavement.

¯ Pavement temperature — more important than air temperature.

This is the first of two columns about what highway departments must consider where snowstorms are an annual event. Next week, part II will discuss the pluses and minuses of using abrasives (sand) or chemicals (salt) to treat our roads in winter.