Frost, ice, sleet/slush, snow or a mixture of precipitation is causing the roadway to be partially covered. Drivers may experience periods when roadway markings are difficult to see. The roadway surface may become slick, snow packed and rutted. Moderate blowing and drifting snow along with occasional drifts may be encountered.
The roadway is completely covered with precipitation. Accumulation is to the point that the roadway markings are most likely obscured, making it difficult to differentiate between the roadway and its surroundings. These conditions could make travel difficult or hazardous.
The roadway has deteriorated to the point that it is very dangerous to travel. Emergency vehicles and snow plows may be called off of the roadway due to the conditions. In the event of an emergency, it may be impossible to get emergency vehicles to the scene.
A road that is impassable is blocked by snow or disabled vehicles. A road that is closed has travel restricted by barricades, fence, gate, official equipment/vehicles or other physical means. Iowa law prohibits motorists from entering a closed roadway or moving traffic control devices.