Procedures for development of CBR design curves

The pattern of design relations for flexible pavements was established and reported in WES Instruction Report 4. This pattern has been modified in recent years and new relations established. This report presents the current procedures for determining flexible pavement thickness requirements. The CBR-thickness relationship can be portrayed by an equation or by a combined CBR curve. This report shows how, by use of equivalent single-wheel loads, the single-wheel design criteria can be applied to any multiple-wheel configuration. Means are also presented for developing either single-wheel or multiple-wheel design criteria for various levels of usage based on load repetitions. A detailed example demonstrating equivalent single-wheel load determinations, pass-per-coverage relationships, and thickness requirements is presented.