Roads can be very slick under which conditions?

Be alert to slick road conditions that may cause your vehicle to skid. Roads are dangerous at the start of a light rain when the water mixes with oil that has not yet washed away from the surface of the road, forming a greasy and slippery film. When there is moisture on the road and the temperature is below freezing, the moisture can turn to ice, causing the roadway to become slippery and dangerous.