In this paper, we provide theoretical structures to present the influence of e-Tag on an individual's total travel cost such that traffic managers can better moderate urban congestion. First, we discuss the substitution effects of these two pricing mechanisms for a simple network structure. Then we demonstrate how the substitution effects of parking fee can reduce urban congestion for more general networks. By using the two-way communication properties of e-tag, vehicles can be detected both on the road and in the parking lots. The insights of using substitution of road tolls and parking fees are further investigated using theoretical models with simple road networks to support the transportation policy making. This paper sheds lights on the substitution effects of these two mechanisms with theoretical analyses, and proposes possibilities for advanced congestion management.