better compaction achieved at little or no extra cost has been shown to improve the performance of dense bitumen macadam. in the present work economically attractive coated macadams of low binder content are shown to have a reduced fatigue resistance but this may be offset by extra compaction. samples of material containing 40 mm maximum size aggregate and 100 pen bitumen were cut from experimental pavements laid in a pilot-scale test facility and were loaded in direct sinusoidal tension and compression until fracture. although fatigue life is shown to be greater at higher test temperatures for a particular strain level this effect is far outweighed by the associated reduction in stiffness. the effect of the type of aggregate in the mixture on its fatigue resistance is small compared with that of the other factors studied. an equation relating laboratory fatigue life, binder content, compaction level and test temperature was developed using a standard multiple regression technique. other aspects of the role of bituminous materials in determining pavement performance require evaluation before roadbases of low binder content can be introduced with confidence. a wider programme of research is therefore being carried out to study other properties related to structural performance.(a)

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