The aggregate used in the pavement should be selected with care, as certain aggregates such as dolomite may polish, or wear smooth under the action of tires. With asphalt pavements and surface treatments, using too much asphalt or asphalt emulsion can cause bleeding or flushing, a condition where excess asphalt rises to the top and fills in the road texture. Both problems increase slipperiness, especially when the pavement is wet.