A method for detecting the operating mode of a hybrid vehicle using roadside cameras, said method including the analysis of thermal images of parts of the vehicle and/or exhaust fumes, in combination with associated images of the number plates obtained using visual camera(s) operating in synchronism with said thermal camera and used for vehicle make inference and driver identification. The inferred make of the car is used for aforementioned analysis of thermal images. In a variant, the method is used to verify an operating mode reported by, or obtained from information reported by, the vehicle itself. The method can be used in a pollution management system for calculating financial charges to vehicle drivers in a low-emission zone of a Smart City for example.