Regarding limitation of fossil fuels and the high consumption rate of their energy for transportation, inclination of vehicle industry toward other sources of energy is inevitable. Electric and hybrid vehicles could be a viable solution. This paper presents quasi-state modeling of hybrid power train components including representations of vehicular dynamics, power-electronic drive, electric motors, energy storage, and other mechanical components. A series hybrid transit bus is developed as a case study. The model is validated using fuel consumption data obtained from tests on an actual hybrid bus.