Street traffic is composed of subsystems, the most important of which are the vehicle, the street, the driver, and the traffic processes. While previous studies have extensively investigated the interactions of the subsystems, the purpose of this paper is to demonstrate methods of considering the entire system as a whole in order to show the comprehensive effect of a given modification.As is shown pictorially, each interaction between all the subsystems must be taken into consideration. The greatest difficulty in modeling the system is the quantification of these interactions. Various sources of this quantification are available.An example of this approach is given. Given the four subsystems mentioned, economic relations between them are identified and quantified. The dependency of total relevant costs on loaded vehicle weight is then analyzed; the relationship between these two variables as determined by the entire system is represented graphically.