Dip. There is a low place up ahead in on the road. In most situations, a dip in the road is harmless. However, you have to watch out for low areas of the road when it is raining or just after the rain. Water may accumulate in the dip and driving through the water at high speeds may cause hydroplaning, a condition when water accumulates under the tire and you lose control of the vehicle. Slowing down when you see a dip road sign is always the safest choice.