Pavement is most slippery in a rainstorm when?

Pavement is most slippery in a rainstorm when it first begins to rain because the initial rainfall mixes with oil and other contaminants that have accumulated on the road surface. This mixture creates a very slippery layer that can be hazardous for vehicles. As the rain continues, this layer may wash away, leading to improved traction. Therefore, the initial moments of rain pose the greatest risk for slippery conditions, making it crucial for drivers to exercise increased caution during that time.