Final answer:
A road is most slippery in winter when ice partially melts and then refreezes, leading to decreased friction. The use of snow tires and deicing salts like sodium chloride and calcium chloride are methods to increase friction and reduce slipperiness on icy roads.
Step-by-step explanation:
Winter Road Slipperiness
During the winter time, a road is likely to be most slippery when the temperature is at or near the freezing point, particularly after a rise in temperature causes ice to partially melt and then refreeze. This creates a layer of water on top of the ice, decreasing the coefficient of friction. This is when road slipperiness is at its peak because tires have less grip on the slick surface.
The use of snow tires is one example of seeking more friction. These tires have specialized tread patterns and rubber compounds designed to grip the road better in cold, icy conditions, compared to standard tires. Understanding that friction is a force that resists motion between two surfaces in contact, safety must maximize this force under slippery conditions.
Cold climates often see the use of deicing salts, such as sodium chloride (NaCl) or calcium chloride (CaCl₂), on roads to prevent ice formation. These salts lower the freezing point of water, helping to melt the ice and reduce slipperiness. By dissolving into ions, these salts disrupt the solid structure of ice, enabling it to transition into a liquid state at lower temperatures and thus, enhancing road safety during winter.