A so-called 'smart card' system is provided with controls which ensure that a request for change in status of a vehicle is not inconsistent with the presence or lack thereof of an appropriate card in the vehicle. As an example, prior to stopping ignition upon the request for stopping ignition, a sensor will look for the presence of a valid card within the vehicle cab. If no valid card is identified, then a warning signal is sent to the operator that no card is within the cab. This will prevent the operator from stopping the vehicle in the event that any appropriate cards have left the vehicle. The operator will thus be saved the inconvenience of having to walk to a location to get another card. In another example, should the request be for locking of the vehicle driver door, the presence of a valid card within the vehicle would be made known to the operator. In this way, the operator will be less likely to lock the card within the vehicle.