How to improve transportation efficiency with latest green communication networking techniques in Intelligent Transportation Systems is a challenging research issue. In this paper, a passenger-based adaptive traffic signal control mechanism is proposed. Three major transportation and green networking related factors including passenger number, pollutant emission and fuel consumption are included in our mechanism. Vehicular messages containing the information of three factors are disseminated among the vehicles and Road Side Units via inter-vehicle and vehicle-to-infrastructure communication. We treat the Road Side Unit as a traffic signal control agent that can adaptively adjust traffic signal cycle in order to transport more passengers with increasing utilization of fuel consumption and reducing of pollutant emission of vehicles. Our mechanism is examined with extensive computer simulations. The simulation results show that the transportation efficiency is improved with up to 23.09% and the fuel consumption and pollutant emission is reduced up to 10.66% with the help of our mechanism.