Access device for a vehicle, having the following features: - an on-vehicle control apparatus ∘ for transmitting enquiry signals to a mobile identification transmitter in order to query the state of motion thereof; ∘ wherein the on-vehicle control apparatus is further configured to adapt the transmission of the enquiry signals for a response from the mobile identification transmitter containing the state of motion thereof or for the absence of the response; - a mobile identification transmitter comprising: ∘ a motion sensor for detecting a movement of the mobile identification transmitter ∘ an identification-transmitter transmitting/receiving apparatus for: + receiving the vehicle's enquiry signals, and + transmitting a response signal containing the state of motion of the mobile identification transmitter in response to at least one enquiry signal ∘ an identification-transmitter control apparatus for controlling the transmission of the response signals (AWO, AW1), characterized in that the on-vehicle control apparatus transmits to the mobile identification transmitter an enquiry signal, containing a request, at any one time or after a specific time interval has elapsed after a specific state of motion of the mobile identification transmitter has been recognized, which enquiry signal forces the mobile identification transmitter to return a response signal in any event. - an on-vehicle control apparatus ∘ for transmitting enquiry signals to a mobile identification transmitter in order to query the state of motion thereof; ∘ wherein the on-vehicle control apparatus is further configured to adapt the transmission of the enquiry signals for a response from the mobile identification transmitter containing the state of motion thereof or for the absence of the response; ∘ for transmitting enquiry signals to a mobile identification transmitter in order to query the state of motion thereof; ∘ wherein the on-vehicle control apparatus is further configured to adapt the transmission of the enquiry signals for a response from the mobile identification transmitter containing the state of motion thereof or for the absence of the response; - a mobile identification transmitter comprising: ∘ a motion sensor for detecting a movement of the mobile identification transmitter ∘ an identification-transmitter transmitting/receiving apparatus for: + receiving the vehicle's enquiry signals, and + transmitting a response signal containing the state of motion of the mobile identification transmitter in response to at least one enquiry signal ∘ an identification-transmitter control apparatus for controlling the transmission of the response signals (AWO, AW1), characterized in that the on-vehicle control apparatus transmits to the mobile identification transmitter an enquiry signal, containing a request, at any one time or after a specific time interval has elapsed after a specific state of motion of the mobile identification transmitter has been recognized, which enquiry signal forces the mobile identification transmitter to return a response signal in any event. ∘ a motion sensor for detecting a movement of the mobile identification transmitter ∘ an identification-transmitter transmitting/receiving apparatus for: + receiving the vehicle's enquiry signals, and + transmitting a response signal containing the state of motion of the mobile identification transmitter in response to at least one enquiry signal + receiving the vehicle's enquiry signals, and + transmitting a response signal containing the state of motion of the mobile identification transmitter in response to at least one enquiry signal ∘ an identification-transmitter control apparatus for controlling the transmission of the response signals (AWO, AW1),