When is the road most slippery during a rainstorm?

The correct answer is the beginning of the storm. During the initial stages of rainfall, the rain mixes with oil and debris that has accumulated on the road surface, creating a slick and hazardous condition. This is particularly true for the first several minutes of rain when the water is not yet sufficient to wash away the oil, leading to reduced traction for vehicles.

Once the rain has been falling for a while, the road generally becomes somewhat safer as the oils are washed away and the surface becomes evenly wet. After the storm ends, while there might still be water present, the most dangerous period for slickness has usually passed. Understanding this timing is critical for adjusting driving behavior during varying weather conditions to maintain safety on the road.