The object of this study is to investigate the layer equivalencies of bases in airport pavements. Seventeen sections of airport test pavements containing various thfcknesses and materials of bases were constructed on sand subgrade. Static and dynamic loadings and traffic tests were carried out on there test pavements by
using a test load cart with dual tandem wheel arrangement and gear load as equal as those of large aircraft.
　After the condition of destruction of test pavements was examined, the layer equivalencies of bases were evaluated on the basis of a lot of test results. The layer equivlaencies calculated on vertical stresses of subgrades should be used in asphalt stabilized materials, cement stabilized materials, lean concrete and slag. Judging from permanent settlements of pavement surface, the laser equivalency of penetration macadam was about the same as that of graded crushed stones. It was ascertained with the help of elastic theories that these values determined from the test pavments could be applied to oadinary airport pavements.
　Besides, some problems on the destruction of airport pavement, the thickness of surface and binder courses, the coverages of aircraft and the design CBR values of subgrades were investigated in relation to the study on the layer equivalencies.