What is a common hazard on roadways during the beginning of rainstorms?

When rain begins to fall, especially after a dry spell, a common hazard that drivers may encounter is the mixture of oil spills and water on the roadway. During dry periods, oil and other substances can accumulate on the pavement. When the rain starts, these substances create a slick, slippery surface, which can lead to reduced traction and an increased risk of losing control of the vehicle. This phenomenon, often referred to as "hydroplaning," is particularly dangerous because drivers may not be immediately aware of how slippery the road has become.

In contrast, excessive speed limits, snow drifts, and fallen tree branches, while they can pose hazards under different circumstances, are not typically associated with the onset of rain. Speed limits are set based on safety regulations and may not change due to rain, snow drifts are more relevant in winter conditions, and fallen tree branches are usually linked to severe weather events rather than the beginning of rain. Thus, the combination of oil and water creates a significant hazard that drivers should be cautious of when it starts to rain.