Local Road Management Manual 457 The soil resilient modulus, MR, is used to relfect the engineering properties of the subgrade (the soil), each time a vehicle passes over pavement and stresses are developed in the subgrade. After the load passes, the subgrade soil relaxes and the stress is relieved. The re- silient modulus test is used to determine the properties of the soil under the repeated load and can be deter- mined by AASHTO test method T274. Measurement of the resilient modulus is not performed by many agen- cies and a relationship between MR and the California bearing ratio (CBR), the more common parameter, is determined instead. The CBR has been widely used to determine the supporting characteristics of soil since the mid-1930’s and a signiifcant amount of historical information is available. The CBR is the ratio of the load-bearing capacity of the soil to the load-bearing capacity of a reference aggregate, multiplied by 100. MR AASTHO also developed the nomograph that follows to solve the foregoing equation. The variables are further deifned in the box that follows.