To alleviate the air pollution problem caused by vehicle emissions, different vehicle inspection programs have been introduced, in which vehicles are examined by undergoing a number of emission tests. However, these emission tests are usually cost-ineffective and time-consuming. It is also difficult to enforce the vehicle owners on monitoring the health of their engines daily and taking immediate action to fix their vehicle emission problems. Therefore, this paper proposes a new vehicle emission inspection and notification system to help daily monitoring of engine health through the concept of Internet of Things. As there are numerous traffic lights in an urban area, they are employed to play an important role in the proposed system. By the fact that every car must stop in front of red lights, reliable reading of air ratio (λ) from a vehicle, which indicates the engine emission status, can be interrogated wirelessly through mature and low-price radio frequency identification (RFID) technology. By inspecting the λ in real time, the vehicle emissions can be effectively controlled by the governmental authorities. Meanwhile, several implementation issues have also been considered and analyzed in this paper. An innovative method is proposed to select the appropriate traffic lights on which RFID monitoring devices should be installed. © 2013 IEEE.