Patent Publication Number: US-6212393-B1

Title: Method and apparatus for communication within a vehicle dispatch system

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates in general to vehicle dispatch systems, and in particular to the communication of assignment messages within vehicle dispatch systems. 
     2. Description of the Related Art 
     A number of vehicle dispatch systems exist for the tracking and controlling of fleets such as taxicabs, delivery trucks, and the like. These systems typically communicate requests for dispatch to the vehicles in the fleet and then match acceptance of the request to the particular request. Key criteria of vehicle dispatch systems, whether manual or automatic, simple or complex, include the system cost, the system performance, and the fairness and timeliness of the selection process. 
     Historically, two-way radio networks have been utilized for vehicle dispatch. Voice communication is the primary communication tool for information gathering and decision making relating to the distribution of assignments in these systems. A dispatch center broadcasts a message of a new assignment location either via a data network or a voice network to the drivers of the various vehicles in the fleet; and each individual driver replies with his/her acceptance or rejection of the assignment to the dispatch center. Typically, the driver&#39;s reply is accomplished via a voice network such as a cellular phone or two-way radio. 
     There are several drawbacks to these vehicle dispatch systems. First, the driver must be alert at all times to listen to the assignment messages from the dispatch center and rapidly determine if the assignment location is within his/her range. The driver must make a quick decision for each message of whether to accept the job or not. In some fleets, if the driver affirmatively replies to the dispatch center and then does not get to the assignment location within a predetermined amount of time he can be fined. The combination of the rapid assignment messaging and decision-making and the potential for fines creates high stress levels in the drivers of the vehicles. 
     A second drawback of the traditional vehicle dispatch systems is that some of the drivers will answer any call, even if not close to the assignment location, motivated by a desire to maximize income or challenge the system. This creates an environment wherein the customer suffers from not receiving the most rapid service. Further, drivers from competing fleets can monitor the frequency of message transmission with a scanner and “steal” the assignments from the drivers who the message was targeted to reach. 
     Further, the broadcast of the assignment message in traditional vehicle dispatch systems is made throughout the entire territory covered by the fleet. In areas where there is a shortage of radio frequency channels, the available channels are rapidly filled to capacity. The expense of maintaining existing channels and/or petitioning the local government for new channels can be out of reach for many dispatch businesses. 
     Today, vehicle dispatch systems designed to alleviate some of the previously described drawbacks typically focus communications and decision-making at the dispatch center. Information such as geographical location and current job status of a selected vehicle is established; and then decisions regarding sending the current dispatch message to that selected vehicle are made by comparing that information either manually or automatically to some predefined criteria in the dispatch center. Automatic vehicle locator systems that automatically track the location of managed vehicles and then report this information to a dispatcher are frequently utilized. Advanced automatic vehicle locator systems further automatically identify the nearest vehicle to a location to further facilitate the dispatcher&#39;s accuracy. In some systems, the geographical location is compared to known locations of authorized vehicles and dispatch of the message is denied to the selected vehicle if the selected vehicle&#39;s location does not correspond to one of the known locations. 
     Other vehicle dispatch systems automatically assign jobs to the closest available vehicle and then inform the driver of the assignment via some other channel, such as the driver&#39;s mobile pager. In this method, no assurance is given that the driver receives the notification or is actually available to take the assignment. The driver actually has no method to decline the assignment in this type of system. 
     The drawback of all of these systems is that the control rests within the dispatch center completely and the complexity of the system communications is increased greatly. Further the channel utilization increases since each call must be sent individually to each selected driver. Lastly, the systems still rely heavily on the dispatcher to make decisions and perform monitoring of the vehicles. This leads to a high degree of errors and confusion. 
     What is needed is a method to reduce the loading of the channels used for vehicle dispatch, reduce the decision-making stress on the vehicle drivers, and at the same time retain the automatic sorting mechanisms of the dispatch center-based systems. 
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
     FIG. 1 is a block diagram of a vehicle dispatch system; 
     FIG. 2 is an electrical block diagram of a wireless communication device for use within the vehicle dispatch system of FIG. 1; 
     FIG. 3 is an illustration of an assignment message for communication within the vehicle dispatch system of FIG. 1; 
     FIGS. 4,  5 , and  6  illustrate various decision-making criteria for use within the wireless communication device of FIG. 2; 
     FIGS. 7,  8 , and  9  are electrical block diagrams of alternate embodiments of the wireless communication device of FIG. 2; 
     FIGS. 10 and 11 are flowcharts illustrating the operation of the wireless communication device of FIG. 2 in accordance with the present invention; 
     FIG. 12 is a flowchart illustrating more detail of the operation of FIGS. 10 and 11; 
     FIG. 13 is a flowchart of the operation of a dispatch center for use within the vehicle dispatch system of FIG. 1; 
     FIG. 14 is an alternate embodiment of the assignment message of FIG. 3; and 
     FIGS. 15,  16 , and  17  illustrate various decision making criteria for use within the vehicle dispatch system of FIG.  1 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to FIG. 1, a vehicle dispatch system  10  for the management of a fleet  12  of vehicles  14  such as taxicabs, delivery trucks and the like is illustrated. The vehicle dispatch system  10  comprises a message input device  24 , such as a telephone or computer terminal, connected through a conventional public switched telephone network (PSTN)  30  by a plurality of conventional telephone links  26  to a dispatch center  16 . It will be appreciated by one skilled in the art that the message input device  24  may also communicate with the dispatch center  16  via alternative communication means such as radio frequency (RF) channels, satellite links, or Internet. 
     The dispatch center  16  functions in a wide variety of manners ranging from fully manual systems to automatic systems employing complex tracking methods. The dispatch center  16  includes a dispatch controller  18 , a dispatch transmitter  20 , and a dispatch receiver  22 . The dispatch controller  18  oversees the operation of the dispatch transmitter  20  and the dispatch receiver  22  through one or more communication links  42 , which typically are conventional telephone links, and additionally can include RF, microwave, or other high quality audio communication links. The dispatch controller  18  encodes inbound requests for dispatch  28  into outbound assignment messages  32 , and decodes inbound replies  38  from the vehicles  14  for matching of a request for dispatch  28  with a vehicle  14  that affirmatively replies. The dispatch controller  18  preferably includes a timer  19  for managing the scheduling of assignments. The dispatch controller  18  schedules the assignment message  32  for transmission by the dispatch transmitter  20 , via a transmit antenna  34 , to each vehicle  14  of the fleet  12  on at least one outbound radio frequency (RF) channel such as a first communication channel  35 . Each vehicle  14  includes a wireless communication device  36  capable of receiving and processing the assignment messages  32 . 
     It will be appreciated that the vehicle dispatch system  10  may function utilizing any wireless RF channel for the first communication channel  35 , for example, a one or two way pager channel, a mobile cellular channel, or a mobile radio channel. In the following description, the RF communication channel refers to any of the wireless RF channels listed above or an equivalent. Each wireless communication device  36  assigned for use in the vehicle dispatch system  10  has an address  48  assigned thereto, which is a unique selective call address. The address  48  enables the transmission of the assignment message  32  from the dispatch controller  18  only to the addressed wireless communication device  36 . The address  48  also identifies the replies  38  sent by the wireless communication device  36  over at least one outbound radio frequency (RF) channel such as a second communication channel  39 ; and received at the dispatch controller  18  through the dispatch receiver  22  via a receive antenna  40 . A list of the assigned addresses for each of the wireless communication devices  36  is stored in the dispatch controller  18  in the form of a vehicle subscriber database. 
     FIG. 2 is an electrical block diagram of a wireless communication device  36  for use within the vehicle dispatch system  10  of FIG.  1 . The wireless communication device  36  includes an antenna  44  for intercepting transmitted signals from the dispatch center  16  of the vehicle dispatch system  10 . The antenna  44  is coupled to a receiver  46  employing conventional demodulation techniques for processing the communication signals received from the dispatch center  16  such as the assignment message  32 . The receiver  46  is capable of receiving and demodulating voice as well as data signals. 
     FIG. 3 is an illustration of the assignment message  32  for communication with the wireless communication device  36  of FIG.  2 . The assignment message  32  preferably includes an address  48 , a location parameter  50 , and a data  52 . The address  48  identifies the wireless communication device  36  for which the assignment message  32  is directed. The location parameter  50  identifies the geographical location of the assignment being transmitted in the data  52  of the assignment message  32 . The data  52  includes all details of the assignment such as customer name, number of passengers, the required time of pick-up, etc. 
     Referring back to FIG. 2, coupled to the receiver  46  is an assignment manager  58  utilizing conventional signal processing techniques for processing the received assignment messages. Preferably, the assignment manager  58  is similar to the MC68328 micro-controller manufactured by Motorola, Inc. of Schaumburg, Ill. It will be appreciated that other similar processors can be utilized for the assignment manager  58 , and that additional processors of the same or alternative type can be added as required to handle the processing requirements of the assignment manager  58 . 
     The assignment manager  58  is coupled to a memory  54  preferably including a random access memory (RAM), a read-only memory (ROM), and an electrically erasable programmable read-only memory (EEPROM). The assignment manager  58  decodes the address  48  in the received assignment message  32 , compares the decoded address with a device address  55  stored in a memory  54 , and when a match is detected, proceeds to process the location parameter  50  of the assignment message  32 . The processing of the location parameter  50  by the assignment manager  58  comprises determining whether to delete the assignment message  32  or process the assignment message  32 . 
     Coupled to the assignment manager  58  is a processor  60 . Preferably, the processor  60  is similar to the MC68328 micro-controller manufactured by Motorola, Inc. of Schaumburg, Ill. It will be appreciated that other similar processors can be utilized for the processor  60 , and that additional processors of the same or alternative type can be added as required to handle the processing requirements of the processor  60 . 
     Once the assignment manager  58  determines that the assignment message  32  should be processed, it sends the assignment message  32  to the processor  60 . Upon receipt of the assignment message  32 , the processor  60  stores the assignment message  32  in the memory  54 . The processor  60  also sends a command to an alerting device  64  to notify the driver of the vehicle  14  in which the wireless communication device  36  is located that the assignment message  32  has been received. In one embodiment, the alerting device  64  comprises a speaker and associated speaker drive circuitry capable of playing both melodies and voice recordings. Upon receiving a command from the processor  60  to play a message receipt alert, the alerting device  64  plays an audible alert. The driver then chooses to review the data  52  of the assignment message  32  on a display screen in the case of data messages or play the recorded voice message in the case of voice messages. 
     The alerting device  64 , in another embodiment, includes a display to generate a visual notification of the assignment message receipt. When the display receives the command from the processor  60  that the assignment message  32  has been received and stored in memory  54 , a message indication is displayed. The message indication, for example may be the activation of one of a plurality of message icons. Selection by the driver of the message indicator associated with the assignment message  32  will display the data  52  of the assignment message  32  on the screen in the case of data messages and play the recorded voice message in the case of voice messages. Alternatively, the data  52  of the assignment message  32  is displayed on the display screen in response to a command from the processor  60  with no required input from the driver. The display may be, for example, a full or partial starburst liquid crystal display. It will be appreciated that other similar displays can be utilized for the display. 
     Preferably, the assignment manager  58  is programmed to include a criteria parameter  62  for comparison of the location parameter  50  of the assignment message  32  with a current location  56  stored in the memory  54 . When the location parameter  50  corresponds to the current location  56 , the assignment manager  58  passes the assignment message  32  to the processor  60  for message processing. 
     The criteria parameter  62  is a pre-set metric for filtering the assignment message  32  received by the wireless communication device  36  to be seen only by the vehicles  14  within the fleet  12  that meet the specified criteria. The criteria parameter  62  may be a calculation, an equation, a function, or a comparison value. The criteria parameter  62  may be changed in response to receipt of a programming message, in response to a timer timeout, or in response to a direct reprogramming of the assignment manager  58 . 
     Utilization of a criteria parameter within an assignment manager included within a wireless communication device greatly reduces the burden of the vehicle driver by filtering out assignments automatically that are outside his/her current range of assignment acceptance. The criteria parameter is programmable and therefor may be changed by the driver or by the fleet manager as required. Further, by placing the decision within the vehicle, the dispatch center is alleviated of the task of tracking each vehicle in the fleet, greatly simplifying the operation of the dispatch center and at the same time reducing traffic congestion on the communication channels. 
     FIGS. 4,  5 , and  6  illustrate various metrics for the criteria parameter  62 . It will be appreciated by those skilled in the art that other metrics may also be used for the criteria parameter  62 . In FIG. 4, the criteria parameter  62  is a perimeter  68  surrounding the assignment location  66  established at a radius  70  from the assignment location  66 . When the wireless communication device  36  receives the assignment message  32  including the location parameter  50 , the assignment manager  58  compares the location parameter  50  corresponding with the assignment location  66  to the current location  56  of the vehicle  14  in which the wireless communication device  36  resides. When the current location  56  is within the perimeter  68 , the assignment message  32  will be sent to the processor  60  for further processing. When the current location  56  is not within the perimeter  68 , the assignment message  32  will be deleted, and the driver of the vehicle  14  would never even be aware that it was received, thereby reducing unnecessary message receipt by the driver of the vehicle. 
     In FIG. 5, the criteria parameter  62  is a driving distance  72  away from the assignment location  66 . Upon receipt of the assignment message  32 , the assignment manager  58  calculates the driving distance from the current location  56  of the vehicle  14  in which the wireless communication device  36  resides to the assignment location  66  that corresponds to the location parameter  50 . When the calculated driving distance is within the driving distance  72  set for the criteria parameter  62  the assignment message  32  will be sent to the processor  60  for further processing. When the calculated driving distance is not within the driving distance  72  set for the criteria parameter  62 , the assignment message  32  will be deleted and the driver of the vehicle  14  would never even be aware that it was received. This process thereby limits the receipt of assignment messages by the vehicle driver to those within a reasonable driving distance. 
     Preferably, the assignment manager  58  includes a navigation program for the area in which the fleet  12  operates. The assignment manager  58  uses the navigation program to calculate the driving distance from the current location  56  to the assignment location  66 . 
     The filtering by driving distance and by perimeter from the assignment location eliminates problems of drivers affirmatively replying to assignment messages clearly outside their range for the purpose of maximizing their own income, thereby enhancing system performance and customer satisfaction. 
     In FIG. 6, the criteria parameter  62  is the travel time  78  equal to the difference between an estimated arrival time  74  and a current time  76 . Upon receipt of the assignment message  32 , the assignment manager  58  determines the estimated arrival time  74  to the assignment location  66 . The current time  76  is subtracted from the estimated arrival time  74  to calculate a travel time. When the calculated travel time is within the travel time  78  assigned to the criteria parameter  62 , the assignment message  32  will be sent to the processor  60  for further processing. When the calculated travel time is not within the travel time  78  assigned to the criteria parameter  62 , the assignment message  32  will be deleted and the driver of the vehicle  14  would never even be aware that it was received. This process thereby limits receipt of assignment messages by vehicle drivers to those that the driver could arrive at within a reasonable timeframe. 
     Preferably, the assignment manager  58  includes a smart program for tracking of traffic conditions coupled to the assignment manager  58 . The smart program calculates the travel time required based on the latest received traffic conditions. Alternatively, the assignment manager  58  may include a program incorporating average travel times and uses the average travel times to calculate the travel time from the current location  56  to the assignment location  66 . 
     The criteria parameter  62  alternatively further includes hours of operation for the vehicle  14 . The hours of operation in one embodiment are set by the driver of the vehicle at the beginning of each shift. Alternatively, the hours of operation are set either manually or automatically via the receipt of a message from the dispatch center. When the estimated arrival time does not fall between the hours of operation, the assignment message  32  will be deleted and the driver of the vehicle  14  would never even be aware that it was received. 
     In another embodiment, the criteria parameter  62  is a type of vehicle that the driver of the vehicle  14  is using at that time. For example, passenger transportation fleets typically include limousines, cars, small cars, vans, and buses. When the location parameter  50  of the assignment message  32  is the number of passengers to be picked up and the criteria parameter  62  is the type of vehicle, the assignment message  32  is deleted if the number of passengers do not fit within that type of vehicle. 
     The examples above illustrate the variety of criteria parameter  62  programmed based on the type of fleet, type of business, and needs of the dispatch center. It will be appreciated by those skilled in the art that other metrics may also be used for the criteria parameter  62 . 
     FIG. 7 is an alternate embodiment of the wireless communication device  36 . The reference numbers of the embodiment of FIG. 2 have been retained for those elements that are common. The wireless communication device  36  of FIG. 7 includes all the elements and functionality illustrated in FIG.  2  and further comprises a transmitter  80  and a device transmit antenna  82 . 
     The transmitter  80  is coupled to the processor  60  and is responsive to commands from the processor  60 . When the transmitter  80  receives a command from the processor  60 , the transmitter  80  sends the reply  38  via the device transmit antenna  82  to the dispatch center  16 . The reply  38  in one embodiment is transmitted over the first communication channel  35 , the same channel used to communicate the assignment message  32 . Using the same communication channel for both sets of communications eliminates the need for multiple channels and is desirable in regions where there is a shortage of available channels. In another embodiment, the reply  38  is transmitted over the second communication channel  39 . Using a different channel for the reply reduces the traffic on the first communication channel and is desirable in regions where the communication channels are congested. 
     The reply  38  preferably includes an affirmative indication to the dispatch center that the vehicle  14  containing the wireless communication device  36  will fulfill the assignment contained within the data  52  of the assignment message  32 . The reply  38  preferably also includes a vehicle identification and the vehicle&#39;s current location  56  and estimated travel time  78  to the assignment location  66 . It will be appreciated that additional information may be included in the reply  38 . 
     FIG. 8 is an alternate embodiment of the wireless communication device  36 . The reference numbers of the embodiments of FIGS. 2 and 7 have been retained for those elements that are common. The wireless communication device  36  includes all the elements and functionality illustrated in FIG.  7  and further comprises a user interface  86 . 
     In the embodiment of FIG. 8, after the processor  60  sends a command to the alerting device  64 , it waits for a user input  84  from the user interface  86 . The processor  60  commands the transmitter  80  to transmit a reply  38  via the device transmit antenna  82  in response to receipt of the user input  84  from the user interface  86 . The user interface  86  may be a button press, a series of button presses, a voice response by the driver of the vehicle  14 , or some other similar method of manual response initiated by the driver of the vehicle to the wireless communication device  36 . 
     Use of the user interface  86  leaves the control of acceptance or rejection of an assignment message with the driver of the vehicle while still filtering assignment messages obviously outside of his/her area. This two step filtering process: the first being automatic by the assignment manager and the second being manual via the user interface, gives the driver of the vehicle control of the matching of assignments, an improvement over the dispatch center—based systems which eliminate all driver control of assignment matches. 
     FIG. 9 is an alternate embodiment of the wireless communication device  36 . The reference numbers of the embodiment of FIG. 2 have been retained for those elements that are common. The wireless communication device  36  includes all the elements and functionality illustrated in FIG.  2  and further comprises a global positioning satellite (GPS) receiver  88  and GPS antenna  90 . 
     The Global Positioning System (GPS) is a worldwide radio-navigation system formed from a constellation of  24  satellites and their ground stations. GPS uses these “man-made stars” as reference points to calculate positions accurate to a matter of meters. The GPS receiver  88  uses the satellites in space as reference points for locations here on earth. The GPS receiver  88  measures distance using the travel time of radio signals. The GPS receiver  88  has very accurate timing to measure travel time. Along with distance, the GPS receiver  88  knows exactly where the satellites are in space. Finally the GPS receiver  88  corrects for any delays the signal experiences as it travels through the atmosphere. 
     The GPS receiver  88  receives a plurality of signals  89  via the GPS antenna  90  corresponding to the current location  56 . The GPS receiver  88  is coupled to the memory  54  and stores the current location  56 , determined from the processing of the plurality of signals  89 , in the memory  54  for later use by the assignment manager  58  as described previously with regards to FIG.  2 . The GPS receiver  88  provides an accurate method for the wireless communication device  36  to determine the vehicle&#39;s current location. 
     FIG. 10 is a flowchart illustrating the operation of the wireless communication device  36  in accordance with the present invention. As indicated in step  92  of FIG. 10, the wireless communication device  36  is normally in the standby mode for optimal power savings. In Step  94 , the wireless communication device  36  periodically checks for receipt of the assignment message  32 . When no assignment message  32  is received, the wireless communication device  36  returns to the standby mode of Step  92 . In Step  96 , when the assignment message  32  is received, the wireless communication device  36  checks for the presence of the location parameter  50  in the assignment message  32 . In Step  98 , when no location parameter  50  is included in the assignment message  32 , the wireless communication device  36  implements whatever default instructions have been programmed into the assignment manager  58  and the processor  60 . The default instruction, for example, may be the processing of the assignment message, the deletion of the assignment message, or the sending of a query for more information from the dispatch center. In Step  100 , when the location parameter  50  is included in the assignment message  32 , the assignment manager  58  compares the location parameter  50  to the current location  56  stored in the memory  54 . When the location parameter  50  does not correspond to the current location  56 , the wireless communication device  36  goes back to Step  92 , the standby state operation. In Step  101 , when the location parameter  50  corresponds to the current location  56 , the processor  60  processes the assignment message  32 . The process then continues to node B as described in FIG. 12 . 
     Processing the assignment message  32  only upon a defined correspondence between the location parameter  50  and the current location  56  greatly reduces the assignment messages being received and processed by each individual driver. This automatic filter ensures the driver only is alerted to assignments in which there is a probability that he/she would be within the scope of the area of the assignment location. 
     FIG. 11 is a flowchart illustrating an alternate operation of the wireless communication device of FIG. 2 in accordance with the present invention. As indicated in step  92  of FIG. 10, the wireless communication device  36  is normally in the standby mode for optimal power savings. In Step  94 , the wireless communication device  36  periodically checks for receipt of the assignment message  32 . When no assignment message  32  is received, the wireless communication device  36  returns to Step  92  in standby mode. When the assignment message  32  is received, the wireless communication device  36  proceeds to Step  96  and checks for the presence of the location parameter  50  in the assignment message  32 . In Step  98 , when no location parameter  50  is included in the assignment message  32 , the wireless communication device  36  implements whatever default instructions have been programmed into the assignment manager  58  and the processor  60 . In Step  102 , when the location parameter  50  is included in the assignment message  32 , the assignment manager  58  compares the location parameter  50  to the current location  56  stored in the memory  54  using the criteria parameter  62  contained within the assignment manager  58 . When the location parameter  50  does not meet the criteria parameter  62  in relation to the current location  56 , the wireless communication device  36  goes back to Step  92 , the standby state operation. In Step  103 , when the location parameter  50  does meet the criteria parameter  62  in relation to the current location  56 , the alerting device  64  is activated. The process then continues to node C as described in FIG.  12 . 
     FIG. 12 is a flowchart illustrating more detail of the operation of FIGS. 10 and 11. Moving from node B to Step  104 , the system checks if the processor  60  is programmed to generate an alert. In Step  103 , when the processor  60  is programmed to generate an alert, the processor  60  sends a command to the alerting device  64  to do so. In Step  106 , when no alert is required or after the alert is generated, the process checks for the presence of the transmitter  80 . When no transmitter  80  is present, the wireless communication device  36  returns to node A and the standby state of Step  92 . In Step  108 , when a transmitter  80  is present, the process checks if the processor  60  is programmed to require the user input  84  from the user interface  86  prior to sending a command to the transmitter  80 . When the user input  84  is required, in Step  110 , the processor  60  looks for the user input  84 . When no user input  84  is detected, the wireless communication device  36  returns to node A and the standby state of Step  92 . When the user input  84  is detected in Step  110 , the processor  60  generates the command to the transmitter  80  to reply to the original assignment message  32 . In Step  112 , the processor  60  checks for the presence of the second communication channel  39 . In Step  114 , When the second communication channel  39  is present, the reply  38  is sent by the transmitter  80  over the second communication channel  39 . The wireless communication device  36  then returns to node A and the standby state of Step  92 . In Step  116 , when the second communication channel  39  is not present, the transmitter  80  sends the reply  38  over the first communication channel  35  in which the assignment message  32  was also communicated. The wireless communication device  36  then returns to node A and the standby state of Step  92 . 
     FIG. 13 is a flowchart of the operation of the dispatch center  16  for use within the vehicle dispatch system  10  of FIG.  1 . In Step  118 , the dispatch center  16  is in a standby state. In the standby state, the dispatch center  16  reduces its operation to draw less current and require less power to operate. In Step  120 , the dispatch center  16  periodically checks for receipt of the request for dispatch  28 . When no request for dispatch  28  is received, the dispatch center  16  returns to the standby state of Step  118 . In Step  122 , when a request for dispatch  28  is received by the dispatch center  16 , the dispatch controller  18  of the dispatch center  16  generates the location parameter  50  identifying the assignment location  66  of the request for dispatch  28 . In Step  123 , the dispatch controller  18  sets the timer  19  for tracking the time for processing of the request for dispatch  28  to matching of the assignment with the vehicle  14 . In Step  124 , the dispatch controller  18  sets a criteria parameter counter to N=1. In Step  126 , the dispatch controller  18  generates the assignment message  32 . 
     FIG. 14 illustrates one embodiment of the assignment message  32 . The assignment message  32  preferably includes the address  48 , the location parameter  50 , a criteria parameter  62  and the data  52 . The address  48  identifies the wireless communication device  36  for which the assignment message  32  is directed. The location parameter  50  identifies the geographical location of the assignment being transmitted in the data  52  of the assignment message  32 . The data  52  includes all details of the assignment such as customer name, number of passengers, the required time of pick-up, etc. 
     The criteria parameter  62 , as described previously, is a pre-set measurement for filtering the assignment message  32  received by the wireless communication device  36  to be seen only by the vehicles  14  within the fleet  12  that meet the specified criteria. The criteria parameter  62  may be a calculation, an equation, a function, or a comparison value. The dispatch controller  18  generates the criteria parameter  62  to be sent in the assignment message  32 . FIGS. 4,  5 , and  6 , previously described, illustrate various metrics for the criteria parameter  62 . It will be appreciated by those skilled in the art that other metrics may also be used for the criteria parameter  62 . 
     Referring back to FIG. 13, in Step  128  the dispatch controller  18  sends a command to the dispatch transmitter  20  to transmit the assignment message  32  via the transmit antenna  34  to each vehicle  14  of the fleet  12  on the first communication channel  35 . The assignment message  32  is then sent to the vehicles  14  of the fleet  12  which each receive the assignment message  32  using the wireless communication device  36 . In Step  130 , the dispatch center  16  checks for receipt of the reply  38  by at least one vehicle  14 . The reply  38  is received by the dispatch center  16  via the receive antenna  40  to the dispatch receiver  22 . The dispatch receiver  22  informs the dispatch controller  18  of receipt of the reply  38 . In Step  132 , when the reply  38  has been received, the dispatch controller  18  resets the timer  19 . The dispatch controller  18  then completes the processing of the assignment match and then returns to Node D and the dispatch center  16  returns to the standby state of Step  118 . In Step  134 , when no reply  38  is received by the dispatch center  16 , the dispatch controller  18  checks for timeout of the timer  19 . When the timer has not timed out, the dispatch controller  18  continues back to Step  130  periodically checking for receipt of the reply  38 . In Step  136 , when the timer  19  has timed out, the dispatch controller  18  sets the criteria parameter  62  to N=2 which typically will relax the criteria to be used for matching the vehicle  14  with the request for dispatch  28 . The dispatch controller  18  then cycles back to Step  126  and generates the new assignment message  32 . 
     FIGS. 15,  16 , and  17  illustrate various calculations of the N=1 and N=2 criteria parameters. In FIG. 15, the criteria parameter  62  is first set at N=1 to a first perimeter  140  surrounding the assignment location  66  at a first radius  142  from the assignment location  66 . The first radius  142  in one embodiment is chosen based on the time of day. For example, during peak hours the first radius  142  is set to a smaller dimension than during non-peak hours. When the wireless communication device  36  receives the assignment message  32  including the location parameter  50  and the criteria parameter  62 , it compares the location parameter  50  corresponding with the assignment location  66  to the current location  56  of the vehicle  14  in which the wireless communication device  36  resides. When the current location  56  is within the first perimeter  140 , the assignment message  32  will be processed. When the current location  56  is not within the first perimeter  140 , the assignment message  32  will be deleted and the driver of the vehicle  14  would never even be aware that it was received. When no reply  38  is received by the dispatch controller  18 , the criteria parameter  62  is set to N=2 corresponding to a second perimeter  144  surrounding the assignment location  66  at a second radius  146  from the assignment location  66 . The second radius  146  is preferably larger than the first radius  142 . When the wireless communication device  36  receives the assignment message  32  including the location parameter  50  and the criteria parameter  62 , it compares the location parameter  50  corresponding with the assignment location  66  to the current location  56  of the vehicle  14  in which the wireless communication device  36  resides. When the current location  56  is within the second perimeter  144 , the assignment message  32  will be processed. When the current location  56  is not within the second perimeter  144 , the assignment message  32  will be deleted and the driver of the vehicle  14  would never even be aware that it was received. When no reply  38  is received by the dispatch controller  18  indicating that no vehicle  14  is located within the second perimeter  144 , the dispatch controller  18  will generate a next criteria parameter (N=3) and continue the process previously described until the reply  38  is received. 
     In FIG. 16, the criteria parameter  62  is first set at N=1 to a first driving distance  148  away from the assignment location  66 . Upon receipt of the assignment message  32 , the wireless communication device  36  calculates the driving distance from the current location  56  of the vehicle  14  in which the wireless communication device  36  resides to the assignment location  66  that corresponds to the location parameter  50 . When the calculated driving distance is within the first driving distance  148  set for the criteria parameter  62  the assignment message  32  will be processed. When the calculated driving distance is not within the first driving distance  148  set for the criteria parameter  62 , the assignment message  32  will be deleted and the driver of the vehicle  14  would never even be aware that it was received. When the dispatch controller  18  does not receive the reply  38 , the criteria parameter  62  is set to N=2 corresponding to a second driving distance  150  away from the assignment location  66 . The second driving distance  150  is preferably larger than the first driving distance  148 . Upon receipt of the assignment message  32 , the wireless communication device  36  calculates the driving distance from the current location  56  of the vehicle  14  in which the wireless communication device  36  resides to the assignment location  66  that corresponds to the location parameter  50 . When the calculated driving distance is within the second driving distance  150  set for the criteria parameter  62  the assignment message  32  will be processed. When the calculated driving distance is not within the second driving distance  150  set for the criteria parameter  62 , the assignment message  32  will be deleted and the driver of the vehicle  14  would never even be aware that it was received. When no reply  38  is received by the dispatch controller  18  indicating that no vehicle  14  is located within the second driving distance  150 , the dispatch controller  18  will generate a next criteria parameter (N=3) and continue the process previously described until the reply  38  is received. 
     Preferably, the wireless communication device  36  includes a navigation program for the area in which the fleet  12  operates. The wireless communication device  36  uses the navigation program to calculate the driving distance from the current location  56  to the assignment location  66 . 
     In FIG. 17, the criteria parameter  62  is first set at N=1 to a first travel time  154  equal to the difference between a first arrival time  152  and the current time  76 . Upon receipt of the assignment message  32 , the wireless communication device  36  calculates its estimated arrival time to the assignment location  66 . The current time  76  is subtracted from the estimated arrival time to calculate a travel time. When the calculated travel time of the vehicle  14  is within the first travel time  154  assigned to the criteria parameter  62 , the assignment message  32  will be processed. When the calculated travel time is not within the first travel time  154  assigned to the criteria parameter  62 , the assignment message  32  will be deleted and the driver of the vehicle  14  would never even be aware that it was received. When the dispatch controller  18  does not receive the reply  38 , the criteria parameter  62  is set to N=2 corresponding to a second travel time  158  to the assignment location  66  equal to the difference between a second arrival time  156  and the current time  76 . The second travel time  158  is preferably larger than the first travel time  154 . Upon receipt of the assignment message  32 , the wireless communication device  36  calculates its estimated arrival time to the assignment location  66 . The current time  76  is subtracted from the estimated arrival time to calculate a travel time. When the calculated travel time of the vehicle  14  is within the second travel time  158  assigned to the criteria parameter  62 , the assignment message  32  will be processed. When the calculated travel time is not within the second travel time  158  assigned to the criteria parameter  62 , the assignment message  32  will be deleted and the driver of the vehicle  14  would never even be aware that it was received. When no reply  38  is received by the dispatch controller  18  indicating that no vehicle  14  is located within the second driving distance  150 , the dispatch controller  18  will generate a next criteria parameter (N=3) and continue the process previously described until the reply  38  is received. 
     Preferably, the wireless communication device  36  includes a smart program for tracking of traffic conditions. The smart program calculates the travel time required based on the latest received traffic conditions. Alternatively, the wireless communication device  36  may include a program incorporating average travel times and uses the average travel times to calculate the travel time from the current location  56  to the assignment location  66 . 
     The invention as described eliminates many of the drawbacks of existing vehicle dispatch systems. The invention reduces the traffic congestion on the communication channels and also reduces the frequency of messages received by the vehicle driver. The invention further reduces the potential for abuse of the system from drivers accepting assignments outside their range of travel. Overall, the system and method described reduces system costs, improves system performance, and improves customer satisfaction, the most important aspects of a vehicle dispatch system. 
     Although the invention has been described in terms of preferred embodiments, it will be obvious to those skilled in the art that various alterations and modifications may be made without departing from the invention. Accordingly, it is intended that all such alterations and modifications be considered as within the spirit and scope of the invention as defined by the appended claims.