Abstract: A method for directing a vehicle from a fleet of N vehicles, numbered n=1, 2, . . . , N(N.gtoreq.2), to respond to a call for assistance received at a central processing station that communicates with a communications unit on each of these vehicles. The central station receives information by radio wave signals on the present location and present status of each vehicle on patrol at a sequence of times. Optionally, the vehicles may be divided into mutually exclusive groups, with each group reporting its location and status at separate times with different frequencies of reporting. An information response interval for a group includes a number of time slots, with each time slot allocated to a vehicle in the group so that no slot is empty. When the central station receives a call for assistance, an assistance message is transmitted to the fleet, specifying the site at which assistance is needed and any available information on the nature of the assistance required.