The initial step in dimension cargo-bearing frames is the determination of loadings. The goal of such dimensioning is to prevent a structural failure during the service-life. The time-dependent loading of cargo in vehicles can be represented by a discontinuous, stochastic, low-frequency process. For analytical purposes, these loadings are approximated by bounded frequency functions from which loading factors and distribution values can be derived.Examples of different vehicle types are given and the periodicity of their loadings are shown. From this data, three different types of loading distributions are seen: approximately symmetrical, a combined symmetrical distribution with a superimposed frequency function, and strongly assymetrical. An analysis of peak values of loading leads to an evaluation of probability of structural failure. These peak values are shown to be caused not only by heavy cargo, but also by poor road surfaces.The paper relates modes of failure to immediate operating conditions and types of long-term service. As such, it offers statistical methods for determining anticipated loading requirements.