What is the effect of rain on road conditions in the first half hour?

When rain first begins to fall, the initial contact with the road surface can mix with oil, dirt, and debris that have accumulated over time. This combination creates a slick layer on the pavement, which significantly reduces tire traction and increases the risk of slipping. As the rain continues, the water can wash away some of this residue, eventually improving traction, but during the first half hour, the roads are especially hazardous.

This understanding is crucial for drivers as adjusting driving behavior during light rain, including reducing speed and maintaining greater following distances, can help to mitigate the risks associated with slippery roads.