Abstract: In the field of vehicle occupant detectors there is a need for an improved vehicle occupant detector which is able to consistently identify the number of occupants in vehicles having windscreens with different infrared transmission characteristics. A vehicle occupant detector comprises a first infrared illuminator that is operable at a first infrared wavelength to illuminate an interior of a vehicle, and a second infrared illuminator that is operable at a second infrared wavelength to illuminate an interior of a vehicle. The vehicle occupant detector also includes a first infrared detector to capture a first image of the interior of the vehicle illuminated at the first infrared wavelength, and a second infrared detector to capture a second image of the interior of the vehicle illuminated at the second infrared wavelength. The first and second infrared detectors have the same infrared detection characteristics.