One embodiment of the invention is directed to automatically populating the cache of a web server. Without imposing additional constraints to ambient carpark illumination, the methodology copes with highly specular vehicle surfaces, ignores non-vehicular objects and detects moving cast shadow or highlight, and adapts to daily and seasonal scene changes, and yet estimates vehicle speed. In response to this request, the system determines if the device is a member of a list of devices for which the sleep proxy takes action. The light receiving unit 2 can thereby receive a sufficient quantity of the incident light 13.