The Dynamic Cone Penetrometer (DCP) is used for rapid in-situ measurement of the structural properties of exsisting road pavement constructed with unbound materials.The unit incorporates an 8 kg weight having a drop of 575 mm, fitted to the end of the shaft is a 20 mm diameter cone. With the standard DCP measurements can be made down to a depth of approximately 850 mm. Readings are usually taken after a set number of blows, changing the number according to the strength of the layer being penetrated. For good granular bases, readings every 5 - 10 blows are satisfactory, but for weaker sub-base layers and subgrades, readings every 1 - 2 blows may be appropriate The DCP requires three operators, one to hold the instrument in a vertical position, one to raise the hammer and let it fall and one to record the results. A typical test takes only a few minutes, providing a very efficient method of obtaining information which would otherwise require the excavation of test pits. Where pavement layers have different strengths, boundaries can be identified and layer thickness determined.