How does the true (user) performance correlate to the measured performance?Ĭalculated the regression coefficients for the PSI equationġ.3 AASHTO Design Equations1.3.1 Performance Requirements & Design Life
Present Serviceability Index (PSI)PSI = A0 + A1F1 + A2F2 + A3F3A0 A3 = Regression CoefficientsF1 = Measure of roughnessF2 = Measure of ruttingF3 = Measure of cracking Measure of RoughnessMeasure of RuttingMeasure of Cracking Measure of how much slope varies from horizontal along the direction of trafficĮstablish correlation between user assessment (ride experience) and performance indicators (measurable characteristics) Measurable characteristics (performance indicators): Visible distress (cracking & rutting) Surface friction Roughness (slope variance) GoodĪ panel of experts drove around in standard vehicles and gave a rating for the pavement
Number of load repetitions with the performance of various pavementsĪASHO Road Test performance based on user assessment: Difficult to quantify (subjective) Highly variable Present Serviceability Rating (PSR)Ġ-1 V. Late 50s road test in Illinois Objective was to determine the relationship between the AMERICAN ASSOCIATION OF STATE HIGHWAY AND TRANSPORTATION OFFICIALSġ.2 Performance MeasurementsEstablishment of performance criteria is critical
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