This paper considers the problem of capacity augmentation in energy efficient road-side unit (RSU) deployments. RSU placements for a road network, and a set of vehicular traffic flow design traces are used as inputs. The objective is to find an RSU radio capacity assignment that minimizes the long-term operating expenditure costs subject to meeting packet deadline constraints with a given packet loss rate target. A procedure, referred to as the capacity augmentation (CA) algorithm, is proposed that iterates over the RSUs, selecting candidates for capacity augmentation based on their packet loss rate sensitivities. A variety of results are presented that characterize and compare the performance of the CA Algorithm using a greedy online packet scheduler. In particular, we show how to counterbalance the lack of causality in designing the RSU network when it is used for the online scheduling of incoming transmission requests. The comparisons include those using energy-optimal offline scheduling obtained by solving an integer linear program (ILP) formulation. It is shown that the CA Algorithm is an efficient way to assign RSU radio capacity that achieves the desired performance objectives.