A method of detecting occupants within a vehicle includes receiving camera data, thermal data and radar data with respect to the vehicle. The received data is stored to at least a first buffer and a second buffer, wherein the first buffer has a length associated with a first duration of time and the second buffer has a length associated with a second duration of time greater than the first duration of time. The camera data, thermal data, and radar data stored in the respective first and second buffers is analyzed to detect and track camera-based objects, radar-based objects, and thermal-based objects, which are utilized to generate an output indicating whether an occupant was detected.