In this paper, an electric powertrain for a bus of rapid transit (BRT) is designed, which includes the driving behavior, road infrastructure, orography, and traffic system as a fundamental part of the design. An electric hybrid power source is proposed to efficiently recover the braking energy and for fast charging at bus stations. Since the local traffic parameters have direct influence over the BRT energy consumption, an energy methodology to obtain a characteristic and energy representative synthetic driving cycle is proposed and then experimentally tested in a real BRT system. The Transmilenio BRT system of Bogotá, Colombia, was chosen as a case study. This BRT system is selected due to its particular orography that increases the energy consumption. Additionally, a BRT dynamic model is proposed to analyze the energy requirements prior to designing the electric powertrain and the two energy storage systems. As a result, and as the main contribution, an innovative general methodology to BRT powertrain design is established using the BRT dynamic model and local traffic parameters.