Abstract:
An odometer monitor for monitoring the connectivity status of a mobile data terminal to a vehicle is a software module defined in a data processor of a vehicle tracking device. The monitor is operable to listen for arrival of successive timed poll events from a mobile data terminal connected to a vehicle, listen for arrival of and storing each of successive odometer update values from a vehicle information bus of the vehicle that corresponds to arrival of each of the successive timed poll events, compare next odometer update values to last stored odometer update values, calculate the distances between the compared odometer update values, make a determination of connectivity status of the mobile data terminal relative to the vehicle based on whether or not the values of the calculated distances ascend to above the value of a preset maximum distance, and report the connectivity status to the mobile data terminal.

Description:
TECHNICAL FIELD 
       [0001]    The subject matter of the present invention is directed generally to employment of a mobile data terminal (MDT) to monitor use of a vehicle and, more particularly, is concerned with a system, method and odometer monitor for detecting connectivity status of the MDT to the vehicle for uncovering un-reported periods of vehicle motion and also determining driver status during such periods. 
       BACKGROUND ART 
       [0002]    An electronic on-board recorder (EOBR) is an electronic device, being one type of mobile data terminal (MDT), attached to a commercial motor vehicle, which is used to record the amount of time a vehicle is being driven. The driving hours of commercial drivers (truck and bus drivers) are regulated by a set of rules known as the hours of service (HOS). HOS rules are intended to prevent driver fatigue, by limiting the amount of time drivers spend operating commercial vehicles. An automatic on-board recorder (AOBR) is another type of MDT that may be used, which is comparable to an EOBR in terms of capabilities. Hereinafter, for the purpose of brevity, the designation MDT will be employed to mean either an EOBR or AOBR. 
         [0003]    In order for the MDT to be considered compliant and useable as required by jurisdictional regulations, the device must be integrally synchronized with the operation of the vehicle so that the device is able to detect when the vehicle is in motion (in other words, be able to track all vehicle motion), and collect odometer data. The MDT must also be able to detect when integral synchronization is compromised (i.e. disconnected), report and record when integral synchronization is compromised, and report and record when integral synchronization is restored. The two reasons for reporting disconnections and reconnections are to inform the driver if/when something fails in the MDT so that appropriate backup actions can be taken, and to inform an inspector when a driver intentionally attempted to hide driving activity (in other words, when the MDT was unable to monitor motion and indicate possible tampering and ghost trip attempts). 
         [0004]      FIG. 1  illustrates a typical prior art vehicle tracking and monitoring system, generally designated  10 . The system  10  meets the aforementioned integrally synchronization requirements with respect to operation of a given vehicle, that is, it can detect when the vehicle is in motion and collect odometer data. In the system  10 , a software application (not shown) running in a user interface (not shown) in a MDT  12  (either in the form of an EOBR or AOBR device) monitors driver status reported through the user interface and also vehicle state data as reported by a vehicle tracking device (VTD)  14 . The MDT  12  records changes in these monitored values as a driver&#39;s record of duty status (RODS), which is recorded in a data store  12 A of the MDT  12  for future display to an inspector. The VTD  14  is interfaced with a vehicle information bus (VIB)  16  and a global positioning system (GPS) receiver  18  by a combination of hardware and firmware (not shown). The VIB  16  is an information network installed in the vehicle, for example by the vehicle manufacturer, which provides access to operational and diagnostic information over standard protocols, such as OBDII, JBUS or CAN BUS. The VTD  14  is a known device commonly referred to as a locator device, which is described in detail in U.S. Pat. No. 7,538,667 issued to same assignee as the subject application. The disclosure of said patent is incorporated herein by reference thereto. 
         [0005]    GPS satellites broadcast signals that can be received and processed by the system  10  to derive latitude, longitude and current time with respect to the location of the vehicle. The GPS receiver  18  includes a processor (not shown) that can receive and interpret the signals broadcasted from the GPS satellites and provide the location (latitude and longitude) of the vehicle and current time. Data processor hardware and firmware of the VTD  14  monitors and interprets signals and protocols from the VIB  16  and the GPS receiver  18  in order to obtain data with respect to the given vehicle such as current Speed, Odometer, Location and Time for use by the MDT  12 . Power is drawn from a vehicle battery  20  for operation of the system  10 . 
         [0006]    Constant power connections via PWR inputs and ignition-switched power connections via IGN SENSE inputs on both the MDT  12  and VTD  14  are made with the vehicle battery  20 . These constant power connections from the vehicle battery  20  to the MDT  12  and VTD  14  are made through respective protective fuses  22 ,  24 . These ignition-switched power connections from the vehicle battery  20  to the MDT  12  and VTD  14  are made through respective protective fuses  26 ,  28 . An ignition switch  30  is operated by the driver of the given vehicle to start and stop the vehicle engine or motor. 
         [0007]    In order to understand where potential problems can arise in detecting the connectivity status of the MDT  12 , first the operation of the system  10  during its Start Up, Monitoring and Shut Down phase need to be described. It is during these phases when disconnection of connectivity, whether intentional or not, is likely to occur. 
         [0008]    The Start Up phase of the system  10  has a VTD startup mode and a MDT startup mode. In the VTD startup mode, the driver activates the ignition switch  30  to start the engine. As a consequence, the VTD  14  detects power on its IGN SENSE input, wakes up from its low power consumption mode, powers up the GPS receiver  18 , and initializes itself. If the VTD  14  does not have an internal battery (which is optional) or at this time its internal battery is exhausted, then the VTD  14  will not have a current time and must initialize its clock from the GPS receiver  18 . Even with the GPS receiver  18  at power, it can still require as much as ten seconds for the GPS receiver  18  to first acquire satellite signals and resolve a location and current time. In the MDT startup mode, the MDT  12  detects the same ignition on event via its IGN SENSE input, wakes up from its low power consumption mode, and displays a user interface to the driver. 
         [0009]    The Monitoring phase of the system  10  has a VTD monitoring mode and a MDT monitoring mode. Once the VTD  14  is powered up and initialized, it starts monitoring vehicle activities. In the VTD monitoring mode, regularly polling of the GPS receiver  18  and VIB  16  occur to obtain current values for Speed, Odometer, Time and Location (Latitude and Longitude). Changes in the Speed are further interpreted by the VTD  14  resulting in a Vehicle State with values of Going or Stopped. In the MDT monitoring mode, after wake-up the MDT  12  polls the VTD  14  for current Time, Location, Vehicle State and Odometer data. When the Vehicle State changes from Stopped to Going, a RODS is recorded in the data store  12 A of the MDT  12  indicating the driver has started Driving. When the Vehicle State changes from Going to Stopped, a RODS is recorded in the data store  12 A indicating the driver is On Duty Not Driving. Every RODS is recorded in the data store  12 A with Time, Location and Odometer values most recently obtained from the VTD  14 . Additional duty status values, not relevant to this discussion, may be inputted by the driver and recorded in the data store  12 A. 
         [0010]    The Shut Down phase of the system  10  has a VTD shutdown mode and a MDT shutdown mode. In the VTD shutdown mode, the driver deactivates the ignition switch  30  to shutoff the engine. As a consequence, the VTD  14  detects power loss on its IGN SENSE input and proceeds to shutdown with a return to its low power consumption mode. A delay exists between detection of the ignition off event and the shutdown but in the end the VTD  14  stops polling the VIB  16  and GPS receiver  18 , powers down the GPS receiver  18 , stops responding to MDT data requests and goes to sleep. In the MDT shutdown mode, the MDT  12  detects the same ignition off event via its IGN SENSE input and initiates a similar shutdown sequence to return to its low power consumption mode. A delay exists between detection of the ignition off event and the shutdown but in the end the MDT  12  stops polling the VTD  14  and goes to sleep. 
         [0011]      FIG. 2  illustrates a modification of the prior art vehicle tracking and monitoring system of  FIG. 1 , now generally designated  10 A. The system  10 A is modified to incorporate a hardware based disconnection monitor in the form of a specialized interconnection cabling  32 A of the connection  32 . The cabling  32 A is used in conjunction with a digital input on the VTD  14  to detect disconnections between the MDT  12  and the VTD  14 . The cabling  32 A includes an additional wire  34  carrying power to a digital input of the VDT  14  from the constant battery power connection to the PWR input of the MDT  12 . The digital input of the VDT  14  is held High (positive voltage) while the MDT  12  is powered and connected. The digital input of the VDT  14  drops Low (zero voltage) when either the MDT  12  is disconnected or the MDT power is removed. 
         [0012]    When the MDT constant battery power to the VTD  14  via the wire  34  of the cabling  32 A is cut by removal of the fuse  22 , the VTD  14  detects the loss of power on the digital input and caches a disconnection event. When MDT constant battery power to the VTD  14  via the wire  34  of the cabling  32  is restored by replacement of the fuse  22 , the VTD  14  detects the power on the digital input and caches a reconnection event. These events are communicated to the MDT  12  and recorded in the data store  12 A of the MDT  12  as Device Disconnection and Reconnection records the next time the MDT  12  establishes communications with the VTD  14 . When the cabling  32 A is disconnected at either end, the VTD  14  detects loss of power on the digital input and caches a disconnection event. When the cabling  32 A is reconnected, the VTD  14  detects power on the digital input and caches a reconnection event. These events are communicated to the MDT  12  and recorded in the data store  12 A as Device Disconnection and Reconnection records the next time the MDT  12  establishes communications with the VTD  14 . 
         [0013]    However, the modified system  10 A is not able to detect when the MDT  12  ignition sense is affected by removal of the fuse  26 . In this case the MDT  12  will remain in power save mode and not track or record changes in vehicle state. Also, the modified system  10 A is not able to detect when the VTD power fuse  24  or ignition fuse  28  are affected. In these cases the VTD  14  is powered off or asleep and the MDT  12  will not be able to track vehicle state changes. Additional features are necessary within the MDT  12  to record when communications fail to the VTD  14 . Further, the modified system  10 A is not able to detect disconnections of the connection  36  between the VIB  16  and the VTD  14 . In these cases the vehicle will appear to not be moving when it is. GPS data could be used in conjunction to detect vehicle motion but GPS jamming will compromise that solution as well. 
         [0014]      FIG. 3  illustrates another modification of the prior art vehicle tracking and monitoring system of  FIG. 1 , now generally designated  10 B. The system  10 B is modified to incorporate a time based polling disconnection monitor  38  in the form of a software module within the MDT  12  to store the time of each poll response received from the VTD  14 . This is called Time of Last Contact. Polling occurs at a fixed frequency so there is an expected period between polls. The duration between polls is compared to the expected poll period. When the duration exceeds the expected period, the polling monitor  38  can assume that a disconnection occurred at some time between the Time of Last Contact and the current poll attempt and record a Device Reconnection record in the data store  12 A of the MDT  12  that also reports when the last contact was. 
         [0015]    When the MDT power at the PWR input or the ignition sense at the IGN SENSE input of the MDT  12  is affected by removal of either the fuse  22  or fuse  26 , the MDT  12  and its polling monitor  38  are not operational. No detection can occur at that time, not until the affected power or ignition sense is restored and the polling sensor of the monitor  38  detects a lengthy period of time elapsed since the Time of Last Contact and produces a Device Reconnection record. This requires use of non-volatile ram to store the Time of Last Contact. When the cabling  32  (see  FIG. 3 ) between the MDT  12  and VTD  14  is disconnected, the polling sensor of the monitor  38  will quickly detect a lengthy period of time since Time of Last Contact and produce a Device Disconnection record. When the cabling  32  is restored, the polling sensor of the monitor  38  is able to detect this as well and produce the Device Reconnection record. When the VTD power at the PWR input or the ignition sense at the IGN SENSE input of the VTD  14  is affected by removal of either the fuse  24  or fuse  28 , the polling sensor of the monitor  38  will quickly detect a lengthy period of time since Time of Last Contact and produce a Device Disconnection record. Restoring the power or ignition sense will also be detected by the polling sensor and a Device Reconnection record produced. 
         [0016]    However, the modified system  10 B is not able to detect disconnections of the connection  36  of the VIB  16  with the VTD  14  and in these cases the vehicle will appear to not be moving even when it is. Additional logic is necessary in the VTD  14  to use GPS data in conjunction with VIB motions to detect vehicle motion but methods of GPS jamming will compromise that solution as well. Furthermore, the modified system  10 B will detect natural power cycles as disconnection and reconnection events which when examined after the fact will make it extremely difficult to distinguish a tampering disconnection and reconnection sequence from a natural power cycle disconnection and reconnection sequence. 
         [0017]    There is therefore a need for an innovation that solves the aforementioned problems of detecting connectivity of the MDT to the vehicle without producing false events that would add noise and make it difficult for an inspector to identify the real tampering and ghost trips. 
       SUMMARY OF THE INVENTION 
       [0018]    The subject matter of the present invention provides such innovation that by employment of the vehicle odometer values can detect if the MDT was disconnected from the vehicle and the vehicle moved during that time by more than a normal (or expected) distance. No problem arises from disconnecting and reconnecting a MDT when the vehicle does not move or moves less than the normal (expected) distance. This typically occurs during maintenance or repairs of vehicle or MDT and it may also occur by accident if a power or data cable comes loose from the back of the MDT. Only when the vehicle is moved is a MDT disconnection a concern for an inspector because while the MDT is disconnected the vehicle motion and driver status goes unrecorded. By interposing an odometer based disconnection monitor approach, any MDT disconnections during time of no vehicle movement or vehicle movement over a distance below the normal (expected) distance will not result in a disconnection event. 
         [0019]    One aspect of the present invention is a system for monitoring the connectivity status of a mobile data terminal to a vehicle. The system includes a vehicle tracking device having an odometer monitor defined in a data processor of the device, a vehicle information bus of a vehicle being connected to the vehicle tracking device and operable to communicate successive odometer update values from the vehicle to the odometer monitor, and a mobile data terminal connected to the vehicle and to the vehicle tracking device and operable to communicate successive timed poll events to the odometer monitor. The odometer monitor is a software module operable to: listen for arrival of the successive timed poll events; listen for arrival of and store each of the successive odometer update values that correspond to arrival of each of the successive timed poll events; compare next odometer update values to last stored odometer update values; calculate the distances between the compared odometer update values; make a determination of connectivity status of the mobile data terminal relative to the vehicle based on whether or not successive values of the calculated distances ascent to above the value of a present maximum distance; and report the connectivity status to the mobile data terminal. 
         [0020]    Another aspect of the present invention is a method for monitoring the connectivity status of a mobile data terminal to a vehicle. The method includes listening for arrival of successive timed poll events from a mobile data terminal connected to a vehicle, listening for arrival of and storing each of successive odometer update values from a vehicle information bus of the vehicle that corresponds to arrival of each of the successive timed poll events, comparing next odometer update values to last stored odometer update values, calculating the distances between the compared odometer update values, making a determination of connectivity status of the mobile data terminal relative to the vehicle based on whether or not the values of the calculated distances ascend to above the value of a preset maximum distance, and reporting the connectivity status to the mobile data terminal. 
         [0021]    Still another aspect of the present invention is an odometer monitor for monitoring the connectivity status of a mobile data terminal to a vehicle. The monitor is a software module defined in a data processor of a vehicle tracking device and operable to: listen for arrival of successive timed poll events from a mobile data terminal connected to a vehicle; listen for arrival of and storing each of successive odometer update values, from a vehicle information bus of a vehicle, that corresponds to arrival of each of the successive timed poll events; compare next odometer update values to last stored odometer update values; calculate the distances between the compared odometer update values; make a determination of connectivity status of the mobile data terminal relative to the vehicle based on whether or not the values of the calculated distances ascend to above the value of a preset maximum distance; and report the connectivity status to the mobile data terminal. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0022]    For clarity, the drawings herein are not necessarily to scale, and have been provided as such in order to illustrate the principles of the subject matter, not to limit the invention. 
           [0023]      FIG. 1  is a block diagram representation of a typical prior art vehicle tracking and monitoring system. 
           [0024]      FIG. 2  is a block diagram representation of a prior art vehicle tracking and monitoring system similar to that of  FIG. 1  but after modification to incorporate a hardware based disconnection monitor. 
           [0025]      FIG. 3  is a block diagram representation of a prior art vehicle tracking and monitoring system similar to that of  FIG. 1  but after modification to incorporate a time based polling disconnection monitor. 
           [0026]      FIG. 4  is a block diagram representation of a vehicle tracking and monitoring system in accordance with the present invention after modification of the prior art system of  FIG. 1  to incorporate an odometer based polling disconnection monitor for detecting connectivity status of the MDT to the vehicle. 
           [0027]      FIG. 5  is a block diagram representation of a portion of the system of  FIG. 4 . 
           [0028]      FIG. 6  is a flow chart representation of the steps of the method performed by the system of  FIGS. 4 and 5  for detecting connectivity status of the MDT to the vehicle. 
           [0029]      FIG. 7  shows graphs of examples of odometer monitor samplings at MDT polling events and of related maximum poll distance when the vehicle is stopped. 
           [0030]      FIG. 8  shows graphs of examples of odometer monitor samplings at MDT polling events and of related maximum poll distance when the vehicle is moving. 
           [0031]      FIG. 9  shows graphs of examples of odometer monitor samplings at MDT polling events with MDT disconnection and of related maximum poll distance when the vehicle is stopped. 
           [0032]      FIG. 10  shows graphs of examples of odometer monitor samplings at MDT polling events with MDT disconnection and of related maximum poll distance when the vehicle is moving. 
           [0033]      FIG. 11  shows graphs of examples of odometer monitor samplings at MDT polling events with VIB disconnection and of related maximum poll distance when the vehicle is stopped. 
           [0034]      FIG. 12  shows graphs of odometer monitor samplings at MDT polling events with VIB disconnection and of related maximum poll distance when the vehicle is moving. 
           [0035]      FIG. 13  is a block diagram representation of an alternative embodiment to that of the vehicle tracking and monitoring system shown in  FIG. 4 . 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0036]    Referring now to  FIG. 4 , there is illustrated a block diagram representation of a vehicle tracking and monitoring system, generally designated  10 C, which incorporates the prior art system of  FIG. 1  but additionally in accordance with the present invention modifies or enhances that system by incorporating an odometer based polling disconnection monitor  40  (hereinafter referred to as the odometer monitor) for detecting connectivity status of the MDT to the vehicle and overcoming the problems associated with the prior art approaches described heretofore. In the portion of system  10 C of  FIG. 4  that is represented in  FIG. 5 , the odometer monitor  40  is a software module defined in a data processor of the VTD  14  that is in communication with both the MDT  12  and VIS  16 , listening for odometer updates and MDT poll events and monitoring the progression of the odometer value. The odometer monitor  40  calculates distances traveled between poll events and is able to recognize when the magnitude of the distance traveled is normal (expected) and when it is abnormal (unexpected) due to events such as: (1) MDT power loss; (2) MDT failure to wake from low power mode (compromised ignition sensing); (3) MDT disconnection from the VTD  14 ; (4) VTD power loss; (5) VTD failure to wake from low power mode (compromised ignition sensing); and (6) VTD disconnection from the VTD  14 . The odometer monitor  40  is also able to distinguish and exclude from recording false disconnections and reconnections events related to normal power cycles. These are excluded because the vehicle typically does not move during these and it is the measuring of distance traveled that is an important feature of the detection method. 
         [0037]    Referring to  FIG. 6 , there is illustrated a flow chart representation of the steps of the method of operation of the odometer monitor  40  of the system of  FIGS. 4 and 5  for detecting connectivity status of the MDT to the vehicle. For distinguishing normal distances from abnormal distances, there are five values that are relevant in the detection method of  FIG. 6 . The first value is the Current Odometer, which is the odometer value most recently reported by the VIB  16  that typically is reported in steps of approximately 500 feet. The second value is the Last Reported Odometer, which is the odometer value last sent to the MDT in a poll response. The third value is the Distance Since Last Poll, which is the distance traveled by the vehicle since the last report of odometer to the MDT  12 . The third value equals Current Odometer minus Last Reported Odometer. The fourth value is the Max Poll Distance, which is the maximum distance the vehicle could travel in the time between two MDT polls. The fifth value is the Current State, which records the current state as Connected or Disconnected. 
         [0038]    As stated earlier above, the odometer monitor  40  is able to calculate distances traveled between poll events (distance per polling period) and also to recognize when the magnitude of the distance traveled is normal (expected) and when it is abnormal (unexpected). The maximum normal distance is the same as the Max Poll Distance. The following is an explanation of how a Max Poll Distance is determined. Since MDT polling occurs at a fixed frequency there is an expected period between polls. Also, every vehicle has a physical maximum velocity. Given these two facts, one is able to determine maximum distance the vehicle could possibly travel during one poll period. With polling frequency given to equal six polls per minute and vehicle maximum speed equal to 120 miles per hour, one can derive a polling period equal to ten seconds per poll and a vehicle maximum speed equal to 176 feet per second. One can then determine the maximum distance per polling period, or the normal (expected) distance, to be equal to 1760 per poll, and distances above this to be abnormal (unexpected) distances. 
         [0039]    Basically, the odometer monitor  40  listens for successive odometer value updates from the VIB  16  via connection  36  and successive timed poll events from the MDT  12  via data connection  32 . Whenever a MDT poll event arrives at the odometer monitor  40  in the VTD  14 , the next odometer value update (Current Odometer value) received at the odometer monitor  40  from the VIB  16  is stored in a memory in the VTD  14  (the odometer monitor  40  will not store an odometer value update from the VIB  16  unless it first receives a poll event from the MDT  12 , a situation as expressed by the graphs in  FIGS. 9 and 10 ), compared to the Last Reported Odometer value by the odometer monitor  40 , and calculate the Distance Since Last Poll value. This calculated distance is compared to the Max Poll Distance value. If, on the one hand, after the last operation of the odometer monitor  40  the system  10 C had been found to be in a connected state and now the Distance Since Last Poll value exceeds the Max Poll Distance value, then vehicle has moved more than would be expected (an abnormal distance) and occurred without the knowledge of the MDT  12 . So the MDT  12  must now be in a disconnected state with the vehicle. However, if, on the other hand, after the last operation of the odometer monitor  40  the MDT  12  had been found to be in a disconnected state with the vehicle and now the Distance Since Last Poll value is within the Max Poll Distance value, then the vehicle has moved with the knowledge of MDT  12 . So the MDT  12  must now be in a reconnected state with the vehicle. As the system  10 C transitions in and out of the connected state Disconnection and Reconnection events are generated and queued within the VTD  14  for transmission to the MDT  12 . 
         [0040]      FIG. 7  illustrates that successive Current Odometer values and Last Reported Odometer values remain unchanged at MDT successive polling events when the vehicle is stopped. Also, the Distance Since Last Poll is unchanged and within the Max Poll Distance when the vehicle is stopped.  FIG. 8  illustrates the successive Current Odometer values and Last Reported Odometer values increase from one to the next at MDT successive polling events when the vehicle is moving and there is no MDT disconnection from the vehicle. Also, the Distance Since Last Poll remains within the Max Poll Distance when the vehicle is moving and there is no MDT disconnection from the vehicle.  FIG. 9  illustrates Current Odometer values and Last Reported Odometer values which include missing Last Reported Odometer values due to interruption of the MDT successive polling events, even though the vehicle is stopped, where there is MDT disconnection. Also, the Distance Since Last Poll is unchanged and within the Max Poll Distance when the vehicle is stopped.  FIG. 10  illustrates Current Odometer values and Last Reported Odometer values which include missing Last Reported Odometer values due to interruption of the MDT successive polling events when the vehicle is moving and where there is MDT disconnection. Also, the Distance Since Last Poll exceeds Max Poll Distance when the vehicle is moving and where there is MDT disconnection.  FIG. 11  illustrates Current Odometer values and Last Reported Odometer values which include missing Current Odometer values due to VIB disconnection when the vehicle is stopped, even though odometer sampling at MDT polling is still occurring. Also, the Distance Since Last Poll is unchanged and within the Max Poll Distance when the vehicle is stopped.  FIG. 12  illustrates Current Odometer values and Last Reported Odometer values which include missing Current Odometer values due to VIB disconnection when the vehicle is moving, even though odometer sampling at MDT polling is still occurring but Last Reported Odometer values during the missing odometer updates remain constant due to the disconnected VIB. 
         [0041]    The following explanation of the operation of the system and method of  FIGS. 4-6  during various disconnection scenarios will further contribute to understanding thereof. In a first scenario, the situation is that the power or ignition sense is compromised at the MDT  12 . In other words, the MDT power is affected by removal of the fuse  22  or the MDT ignition sense is affected by removal of the fuse  26 . In these cases, the MDT  12  is not operational and ceases sending regular polling requests to the VTD  14 . This will result in the odometer monitor  42  within the VTD  14  to stop updating the Last Reported Odometer values and if the vehicle starts moving the Distance Since Last Poll values will soon exceed the Max Poll Distance value, resulting in a disconnection event. When the removed fuse  22  or  26  is replaced, the MDT  12  will become operational and start polling the VTD  14 . This will cause the odometer monitor  40  to regularly update the Last Reported Odometer values. Soon thereafter the Distance Since Last Poll value will be calculated and will be within the Max Poll Distance value or threshold, resulting in a reconnection event. The first scenario is depicted in the graphs of  FIG. 9  when the vehicle is stopped and graphs of  FIG. 10  when the vehicle starts moving. 
         [0042]    In a second scenario, the situation is that the data cable connection  32  between the MDT  12  and the VTD  14  is disconnected at either end. In this case, the MDT  12  is powered and operational and attempting to send regular polling requests but these are failing due to the disconnection. The MDT  12  can warn the driver of this situation immediately so the driver can take corrective backup action. The VTD  14  stops receiving poll requests and the effects and outcomes are the same as in the first scenario, namely, a disconnection event. When the connection  32  is re-established (data cable is replaced or reconnected), the polling is re-established to the VTD  14  and the outcome is the same as in the first scenario, namely, a reconnection event. 
         [0043]    In a third scenario, the situation is that the power or ignition sense is compromised at the VTD  14 . In other words, the VTD power is affected by removal of the fuse  24  or the VTD ignition sense is affected by removal of the fuse  28 . In these cases, the VTD  14  is not operational and does not respond to MDT poll requests. The MDT  12  can warn the driver of this situation immediately so the driver can take corrective backup action. The odometer monitor  40  is also not operating and unable to produce a disconnection Event, so the disconnection event will be produced at reconnection. When the removed fuse  24  or  28  is replaced, the VTD  14  and odometer monitor  40  become operational. The first odometer update arriving from the VIB  16  will result in a large Distance Since Last Poll value calculation that exceeds the Max Poll Distance (if the vehicle was moved significantly during the disconnection) resulting in a disconnection and reconnection event. 
         [0044]    In a fourth scenario, the situation is that communication of the VTD  14  with the VIB  16  is compromised. In other words, the cable connection  36  between the VIB  16  and VTD  14  is disconnected. In this case, the VTD  14  is operational and responding to MDT poll requests but is unable to update Current Odometer values. The VTD  14  can detect this situation and report it to the MDT  12  so that the driver can take corrective backup action. The odometer monitor  40  is operating but will be unable to produce a disconnection event at this time because the Current Odometer value is not updating and will not result in increasing the Distance Since Last Poll value. This disconnection event will be reported at reconnection. When the connection  36  is re-established, the first odometer update arriving from the VIB  16  will result in a large Distance Since Last Poll value calculation that exceeds the Max Poll Distance value (if the vehicle was moved significantly during the disconnection), resulting in a disconnection and reconnection event. The fourth scenario is depicted in the graphs of  FIG. 11  when the vehicle is stopped and graphs of  FIG. 12  when the vehicle starts moving. 
         [0045]    Referring now to  FIG. 13 , there is illustrated a block diagram representation of a vehicle tracking and monitoring system, generally designated  10 D, which is an alternative or modified embodiment to that of  FIG. 4 . The system  10 D of  FIG. 13  does not include a separate VTD  14 . Instead, the system  10 D incorporates the functionality of the VTD  14  and its odometer monitor  40  within the MDT  12 . This alternative embodiment eliminates one-half of the potential disconnection points and cases as the following cables and connections to the VTD  14  are no longer exposed via cables: (1) data cable  32 ; (2) power connections and fuse  24 ; and ignition sense connection and fuse  28 . Also, the GPS receiver  18  is now connected to the MDT  12 . The polling between the MDT  12  and the VTD  14  still occurs, but not exteriorly; it is now contained interiorly or entirely within the MDT  12 . 
         [0046]    It should be understood that in light of the foregoing description and in the claims that follow the recitation of the VTD  14  as a “device” and as being “connected” to the MDT  12  and to the VIB  16  is meant to be interpreted to cover the instance where the VTD  14  is provided as a separate entity as per  FIG. 4  as well as the instance where the VTD  14  is not as a separate entity as per  FIG. 13 . 
         [0047]    In the description herein, embodiments disclosing specific details have been set forth in order to provide a thorough understanding of the invention, and not to provide limitation. However, it will be clear to one having skill in the art that other embodiments according to the present teachings are possible that are within the scope of the invention disclosed. All parameters, dimensions, materials, and configurations described herein are examples only and actual values of such depend on the specific embodiment.