Road lighting is a key factor for traffic safety and visual comfort, but also represents a significant share of urban energy consumption. Numerous optimization methods have been proposed to design more efficient installations; however, their results are difficult to compare because they rely on different input models, lighting standards, and problem formulations. Thus, a common formal representation is needed that enables comparison not only of optimization algorithms but also of their normative and contextual assumptions. This paper introduces the Infrastructure Abstract Graph (IAG), a typed attributed graph model that can represent the road lighting infrastructure in a way that is independent of any particular optimization method. The approach is illustrated in a real case study, where an existing urban lighting network is mapped to IAG and three different optimization strategies are applied. The example demonstrates how IAG supports systematic comparison of methods and the resulting design configurations.