Anyone that has spends time on the roads is probably well aware of the danger posed by potholes and broken pavement. Left unattended, they can easily cause a tire to puncture, which can present multiple problems. This can result in the relatively minor inconvenience of a flat tire or a more significant problem of a tire that blows out. In addition to the potential for problems with a car’s tire, the process of going over a pothole or uneven pavement can cause a driver to lose control of their car, which poses obvious problems for other drivers sharing the road. Winter weather creates particular problems for road maintenance, both because potholes are more likely to form and because they might be obscured by weather conditions like snow. What causes potholes to form in the first place?
The basic cause of potholes relates to moisture and breaks in the pavement surface. Throughout the year and regardless of local weather, potholes can form if moisture seeps into the ground that is supporting the road in question through cracks in the pavement. With the supporting ground structure weakened, roads might not be able to support the weight of numerous cars in even moderate traffic. A localised version of this might create a pothole, but if the situation is particularly bad a sinkhole could lead to even greater disruptions, traffic chaos, and even loss of life.
In winter, cold weather and the freezing/thawing process common to many areas can create further problems. If cracks in the pavement allow water to seep into the supporting ground surface, cold weather can cause this water to freeze. As water freezes, it expands; think of an ice cube tray with room temperature water compared to the same tray after the tray has become frozen after an hour or two in the freezer. This process means that small cracks can become larger as the moisture gathers and freezes inside these cracks, which can cause a pothole.
The same process applies to water that seeps into the surrounding ground, with even more significant consequences. When ice in the surrounding ground melts and returns to its normal level, pavement that had been swollen by the (expanded) frozen ground is left unsupported. Regular pressure and weight from road traffic over these areas can cause the expanded, unsupported pavement to collapse. The result is a pothole, and potentially a major one if the area in question is large and receives regular or heavy traffic.
Another way that winter weather creates potential potholes is through the use of salt on roads. When salt is added to water, it lowers the temperature at which water freezes. This can keep roads free of dangerous ice or accumulated snow when applied prior to the arrival of a winter storm. However, in addition to causing damage to the environment surrounding the salted road itself, this unfrozen water/salt combination must go somewhere. If this ends up in between exisiting cracks in the pavement, they can cause more damage through the freezing/thawing process described earlier.
Winter weather can also cause issues with the overall process of normal drainage from high-use areas like roads. In addition to the problem of drains and pipes freezing and preventing proper flow of water away from roadways, a drain can easily be blocked if a tree branch falls due to ice accumulation during a storm. In areas with early frosts, pipes can also become clogged with leaves in the autumn and then freeze. This could result in blocked and potentially burst pipes, which themselves can cause major damage to the integrity of the pavement and create conditions that lead to potholes.
Winter weather presents numerous issues related to potholes, some of which are unavoidable. The nature of the freezing/thawing process and the impact this has upon pavement means that even minor cracks in the surface can have significant impact. An understanding of how and why winter poses particular problems will hopefully lead to fewer potholes and less negative impact on drivers, their vehicles, and roads themselves.