How do roads behave during the first few minutes of rain?

During the first few minutes of rain, roads become more slippery primarily due to the presence of oil and grime that has accumulated on the pavement. When rain begins to fall, it mixes with these substances, creating a slick surface that can reduce traction for vehicles. This is particularly true for asphalt roads, as the initial rain can cause the oils to float on the water's surface, leading to slippery conditions. Drivers need to exercise caution during this period, as their stopping distances can increase and their control over the vehicle may be compromised. Once the rain continues for a while, it can help wash away these oils, leading to improved traction, but the initial moments following the onset of rain present the greatest risk.