It is essential for car manufacturers to ensure their vehicle robustness under a daily usage. As no detailed method nor standard prevails, each manufacturer is expected to setup its own methodology for safety parts life-assessment. The early stages of a renewed methodology are proposed in this study. This is based on proving-grounds measurements analysis to quantify the impact of various loads. The method, developed from the load measured at the vehicle wheels, considers the multi-input load case and its variable amplitude content. Measured time-series are analyzed and partitioned into two main categories depending on the time-correlation between the load axes. The driver-induced loads, Driven-Road, (DR) loads, are separated from the effects of random road conditions, Random-Road, (RR) loads. Then, for partition validation, a suitable life quantification method is applied in parallel to the two types of loading. On one hand, an assumption based on strong physical meaning eases the Rainflow Counting method application on the DR load. On the other hand, the use of spectral methods is explored to handle the random loads. This paper details the partition process of the time-series and each of the subsequent validation steps of the method to apply such a partition. Such a validation is performed via a comparison of the pseudo-damage between a referenced signal and the one issued from the partition.