A study was made of proposed means by which water can enter chipseals surfaces and induce flushing. The means were water transfer from the basecourse and pressure from tyres on wet roads. The data support the occurrence of both phenomena. It is possible that a significantly greater proportion of chipseal surfaces than is commonly believed are in fact permeable to water.
Further research is suggested to gain additional information on the flushing process, to assess the prevalence of permeable seals, to devise means of assessing seal sites for their susceptibility to water induced flushing, and to develop ways of countering this phenomenon.
Keywords: chipseal, flushing, water, permeability, New Zealand, roads