Patent Publication Number: US-8112219-B2

Title: System for and method of monitoring real time traffic conditions using probe vehicles

Description:
TECHNICAL FIELD 
     The present invention relates to systems for and methods of collecting traffic data using probe vehicles, and more particularly, to a system for and method of delivering traffic data to a plurality of vehicles and selectively updating the traffic data using a plurality of probe vehicles and a traffic information center. 
     BACKGROUND OF THE INVENTION 
     It is known in the prior art to use vehicles as probes for measuring traffic conditions in real-time. Individual vehicles provide “floating car data,” such as, for example, the vehicle&#39;s time, speed, position, and heading, which can be used to estimate travel time and traffic speed, and which can in turn be used as an online indicator of road network status, as a basis for detecting incidents, or as input for a dynamic route guidance system. 
     With reference to  FIG. 1  (PRIOR ART), an exemplary prior art probe vehicle system  10   a  typically includes a plurality of probe vehicles  12   a ; technology  14   a  for determining each probe vehicle location, such as, for example, a system using orbiting satellites, such as the Global Positioning System (GPS), a system using cellular telephones, or a system using radio-frequency identification (RFID); and a wireless communication system  16   a  for allowing communication between the vehicles  12   a  and a traffic information center (TIC)  18   a . Typically, the center  18   a  receives and processes the data generated by the probe vehicles  12   a , and then transmits the data to a plurality of receiving vehicles, which may further include non-probe vehicles  20   a . Constant communication between the probe vehicles  12   a  and the center  18   a  requires the storage of a voluminous amount of data. 
     One type of traffic control system categorizes geographic thoroughfare sections as links and utilizes generally constant probe vehicle data within a set of link coordinates to reach a general link condition. Other receiving vehicles located upon the link receive the pre-determined general condition, which is constantly being updated by the probe vehicles upon the link. Using traffic simulation methods, different studies have provided widely varying estimates of the number of probe vehicles needed to accurately determine a general link condition. These studies indicate that, on a freeway, for example, 2% to 7% of the vehicles present must be probe vehicles providing data in order to determine real-time traffic conditions with a sufficiently high level of confidence. Even in this configuration, however, an exceedingly large number of probe vehicles are typically required to communicate with the center to transmit and store large amounts of data; and here, again, exceedingly substantial data processing capacity remains necessary at the center to process a large volume of incoming data in real-time. 
     In another prior art configuration, the transmission of traffic data between the center and vehicles is reduced by limiting transmissions to instances where one of a pre-determined set of conditions is achieved. In other words, the probe vehicle communicates traffic data to the center only when sensors indicate that at least one of a plurality of triggering conditions exist. However, like the other traffic control systems, this configuration requires that large sets of data, i.e. pre-determined triggering condition data, be stored on-board each probe vehicle. 
     SUMMARY OF THE INVENTION 
     Responsive to these and other concerns presented by conventional probe vehicle traffic control systems, the present invention presents a traffic control system for and method of selectively updating and transmitting traffic data to a plurality of receiving vehicles upon a link. Among other things, the present invention is useful for reducing the amount of transmitted and on-board stored data during traffic control operation. The reduction in data management enables the available system resources and capacity at both the traffic control center and participating vehicles to be reduced, and the reduced traffic further provides a more efficiently operating and faster communication system. 
     A first aspect of the invention concerns a traffic control system for updating and communicating at least one condition to at least one receiving vehicle upon a thoroughfare. The system includes a data control center configured to determine and store a first value of the condition, and at least one probe device communicatively coupled to the center, and configured to determine a probed value of the condition. The center is configured to transmit to said at least one probe device the first value of the condition. Each probe device is further configured to compare the first and probed values of the condition, so as to determine a condition discrepancy, and transmit the probed value to the center, where the discrepancy is greater than a pre-determined discrepancy threshold. The center is further configured to modify the first value of the condition upon receipt of the probed value from said at least one probe device, and transmit the modified first value to said at least one receiving vehicle. 
     A second aspect of the present invention concerns a traffic control system for updating and communicating at least one condition to at least one receiving vehicle upon a link, wherein said link is pre-defined. In this embodiment, the data control center further includes a map database of a plurality of links, and is configured to determine and store a first value of the condition for each link. The center is further configured to periodically transmit to said at least one probe device an electronic copy of the database. The probe device is further configured to determine its current position upon the map database. Finally, the center is configured to modify the first value of the condition upon receipt of the probed value from the probe device, and transmit a modified database to at least one receiving vehicle. 
     Thus, it will be appreciated and understood that the system and method of the present invention provides a number of improvements and advantages over the prior art, including for example, reducing on-board data storage requirements, the number of simultaneous communication channels required to report probe vehicle data to the receiving center, and reducing the amount of such data which must be processed in real-time at the receiving center. 
     These and other features of the present invention are discussed in greater detail in the section below titled DESCRIPTION OF THE PREFERRED EMBODIMENT(S). 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A preferred embodiment of the present invention is described in detail below with reference to the attached drawing figures, wherein: 
         FIG. 1  (PRIOR ART) is a depiction of a prior art system for collecting traffic data using probe vehicles, wherein each of a plurality of probe vehicles operates substantially independently and separately reports its local traffic data to a receiving center; 
         FIG. 2  is a plan view and block diagram of a preferred embodiment of a probe vehicle in accordance with a preferred embodiment of the invention; 
         FIG. 3  is a depiction of a traffic control system in accordance with a preferred embodiment of the present invention, particularly illustrating a TIC receiving data from probe vehicles, and transmitting data to receiving vehicles; 
         FIG. 4  is a plan view of a second preferred embodiment of the system, wherein the probe vehicles first communicate with a probe device communicatively coupled to the TIC; 
         FIG. 5  is a flow chart of a method of collecting traffic control data using probe vehicles in accordance with a preferred embodiment of the present invention; 
         FIG. 6  is a plan view of a preferred embodiment of the system including a receiving center, locator device, and pluralities of probe and receiving vehicles upon a link; and 
         FIG. 7  is a plan view of a third preferred embodiment of the system, wherein the system includes a plurality of communicatively coupled centers each further communicatively coupled to a separate set of probe vehicles. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT(S) 
     The present invention concerns an improved traffic control system  10  adapted for use with a vehicle  12 , and by an operator  14 . The system  10  further includes a central Traffic Information Center (TIC)  16 , and wireless communication means  18  for bilaterally delivering electronic signals between the TIC and vehicle  12 . In general, the inventive system  10  is configured to relay a first value of a traffic or other type of condition to the vehicle  12 , and modify the first value by selectively receiving updates based on a comparison of the first value and a determined second value. The system  10  is described and illustrated herein with respect to an automotive vehicle (see,  FIG. 2 ), however, it is appreciated by those ordinarily skilled in the art that the system may be used in conjunction with other devices, transportation machines and modes, such as boats, aircrafts, and human motility. The function and operation of the system  10  is described herein with respect to one vehicle  12 , however, it is further appreciated that the preferred TIC  16  is configured to concurrently communicate as described with a plurality of properly configured vehicles  12 . 
     In a preferred embodiment shown in  FIGS. 3 through 5 , the system  10  functions to periodically broadcast current anticipated condition values, such as the average travel speed of a pre-defined thoroughfare section or link  20  to a plurality of vehicles  12 . In this configuration, the TIC  16  is configured to maintain and transmit to the vehicles  12  at least a portion of a map database (not shown), either continuously, periodically, or upon request. The map database comprises of a plurality of interconnected links  20 , wherein each link  20  is associated with current anticipated values for at least one condition. Each vehicle  12  is preferably configured to receive and store an electronic copy of at least a portion of the database in a storage device  22 , so as to present a vehicle map. 
     The system  10  further includes a locator device  24  that is configured to locate the position of at least a portion of the vehicles  12  upon the vehicle map. For example, as shown in  FIG. 3 , for each such vehicle the locator device  24  may include a Global Positioning System (GPS) receiver  26  communicatively coupled to orbiting satellites. Alternatively, the locator device  24  may utilize a dead-reckoning system, network of cellular telephones, or a system using radio-frequency identification (RFID). When a vehicle  12  is positioned upon a link  20 , the corresponding anticipated value of the condition is identifiable by a vehicle controller  28 . 
     These locatable vehicles are further configured to selectively provide feedback to the TIC  16 , so as to present probe vehicles  12   p . Each probe vehicle  12   p  is configured to determine a second value of the condition. More preferably, each probe vehicle  12   p  includes at least one sensor  30  that is communicatively coupled to the controller  28  and configured to detect an actual value of the condition. The controller  28  is further configured to compare the anticipated and actual values, so as to determine a condition discrepancy. The preferred comparison algorithm may determine a percentage ratio, absolute difference or combination thereof to determine the condition discrepancy. The discrepancy is then compared to a discrepancy threshold. Finally, to provide adjustability where desired (i.e. less traveled versus crowded links), the comparison algorithm and/or threshold are preferably modifiable by either the operator  14  or TIC  16 . More preferably, a comparison algorithm factor or the threshold may be automatically adjusted to a link factor or link threshold, once the vehicle  12   p  enters the link. 
     The probe vehicle  12   p  includes suitable transmissions means for transmitting the actual value back to the TIC  16  center, when the discrepancy exceeds the threshold. More preferably, the probe vehicle  12   p  includes a long range wireless communication processor or communicator  32  that is capable of real-time processing and transmission. Suitable transmission technology for this purpose include cellular data channels or phone transmissions, broadcast technologies, such as FM/XM frequencies, local and nation-wide wireless networks, such as the Internet, and mobile radio communication systems, such as GSM (Global System of Mobile Communication), GPRS (General Packet Routing System), and UMTS (Universal Mobile Telephone System). Where at least one intermediary amplification or repetitive probe station  34  is incorporated as shown in  FIG. 4 , additional shorter range technologies, such as a Dedicated Short Range Communication (DSRC) system or a Short Message System (SMS), may be utilized by the probe vehicles  12   p . In this configuration, the intermediary probe station  34  preferably includes the long-range communicator  32  and communicates with the TIC  16 . The TIC  16  may be configured to communicate directly back to the vehicles  12  or as shown in  FIG. 4 , also through the station  34 . Finally, in a preferred embodiment, the medium- to long-range communication capability of the communication processor  32  may only be enabled when and while the probe vehicle  12   p  is in a pre-determined condition (e.g. in gears greater than second) and disabled at all other times. 
     The communication processor  32  is provided with a pre-defined message protocol for accomplishing the functions relating to operation of the present invention. Implementation of the communication processor  32 , and particularly the message protocol, can involve substantially conventional techniques and is therefore within the ability of one with ordinary skill in the art without requiring undue experimentation. 
     Thus, the implemented probe vehicles  12   p  download the data for the link upon which they are traveling and compare the anticipated TIC data to its own speed, position (e.g., latitude and longitude, and heading) or other applicable parameter. If there is a significant discrepancy between the downloaded data and the actual comparable data, the probe vehicle  12   p  reports the discrepancy to the TIC  16  by uploading the actual speed, position or other discrepant data. If there is no discrepancy, no transmission to the TIC  16  is performed. By limiting the transmissions to discrepancies only, it is appreciated that the frequency and volume of data that must be uploaded from the probe vehicles  12   p  is reduced. This in turn reduces the number of simultaneous communication channels required to report the data to the TIC  16  and reduces the amount of data, which must be processed in real-time at the TIC  16 . It is also appreciated that comparing data received from the TIC  16  and reporting only the significant discrepancies reduces probe vehicle onboard data storage requirements. 
     The actual data are collected and considered to update the database at the TIC  16  and is therefore used to generate a new anticipated condition. This actual feedback data can be used in sophisticated algorithms as a function of such major parameters as: time of day, day of the week, current or expected weather conditions, occurrence of construction or sporting events, and other relevant factors in the area around a given link to determine the anticipated conditions. Other inputs such as third party data entry at the TIC  16 , physical relationships and computational conclusions based on road geometry and other parameters, as well as historic data may also be utilized to determine or refine the anticipated value of the condition. 
     Once probe vehicle feedback data has been collected for a pre-determined period (i.e. 5 minutes, 30 minutes, etc.), depending upon the volatility of the condition, and the anticipated value of the condition has been updated, the TIC  16  is configured to re-transmit the updated anticipated values to the designated receiving vehicles  12 . 
     In addition to or lieu of the speed condition described herein, the system  10  may be configured to determine other discrepant conditions, such as excessive lateral acceleration (LA) where slippery conditions are present (i.e. where rain is sensed). In an LA determining configuration, previously anticipated safe driving conditions may be transmitted to a probe vehicle  12   p  on a curved link by the TIC  16 . The probe vehicle  12   p  determines corresponding actual conditions, such as vehicle velocity, lateral velocity, and sideslip angles by a plurality of sensors (not shown). Where a discrepant vehicle velocity upon a curve during a rainfall event is not accompanied with anticipated discrepant lateral velocity and/or sideslip feedback, the driving conditions may be transmitted to the center and updated to reflect a less dangerous road state. It is appreciated, however, that this configuration may require a larger factor of safety given the vast differences in vehicle handling capabilities. 
     In exemplary but non-limiting use and operation, a method of performing the present invention, wherein only the anticipated values of a selected condition are transmitted to receiving vehicles  12  located upon a link  20  may be implemented to function as follows. Referring to  FIG. 5 , the method begins at a step  100  wherein the threshold is set for probe vehicles  12   p . At a step  102 , the TIC  16  determines the location of the vehicle  12  preferably through communications means  18 . Next, at a step  104 , it is determined whether the position of the vehicle  12  corresponds to a link  20  upon the map database. If the vehicle  12  is not positioned upon a link  20 , the method returns to step  102  as the vehicle travels. Otherwise, the method continues to parallel data consideration steps shown as  106   a - c  in  FIG. 5 , wherein link specific data are determined or received. At step  108  the anticipated value of the condition is determined from any combination of parallel steps  106   a - c , and at step  110  is transmitted to the vehicle  12 . 
     At step  112 , whether the vehicle  12  further presents a probe vehicle  12   p  is determined. If the vehicle  12  is also a probe vehicle  12   p , the method proceeds to step  114  where the probe vehicle  12   p  determines an actual value of the condition and compares the actual and anticipated values to determine a condition discrepancy. For example, as shown in  FIG. 5 , the absolute difference between the actual and anticipated values can be determined. If the vehicle  12  is not a probe vehicle  12   p  then the method skips ahead to step  120  and undergoes a waiting period prior to returning to step  102 . 
     At step  116 , the probe vehicle  12   p  compares the condition discrepancy to a discrepancy threshold to determine a non-compliant actual condition. If the threshold is exceeded, the probe vehicle  12   p  transmits probed data to the TIC  16  for consideration at step  118  in determining future anticipated values of the condition. Step  118  is preferably performed in parallel to steps  106   a - c , so that a new anticipated value can be determined solely from the received actual probe values or from a combination of probe values and the other data considerations. The probe data preferably includes the actual value, as well as the probe vehicle position, time, date, and day of the transmission. If the discrepancy does not exceed the threshold, then the method proceeds to step  120 , and undergoes the waiting period prior to returning to step  102 . It is appreciated that the waiting period provides sufficient time for a useful sample of probe vehicle data to be received and utilized to refine the anticipated values. 
     In an alternative embodiment, the TIC  16  may be configured to transmit the first value to the vehicle  12  only upon request from the vehicle  12 . In this configuration, at step  102 , the TIC  16  determines the location of the vehicle  12  preferably by receiving the position data from the vehicle  12  along with the request for information. More particularly, the TIC  16  may be further configured to determine and store first values of anticipated speeds for a plurality of thoroughfares upon a map database, and the vehicle  12  may be configured to receive a route request from the operator  14 , and transmit the request to the TIC  16  (see,  FIG. 6 ). Upon receipt, the TIC  16  is configured to determine and transmit the route and anticipated speed data along the route back to the vehicle  12 . As previously discussed, where the vehicle  12  further presents a probe vehicle  12   p , actual speed data can be determined, compared to the anticipated speed data received, and fed back to the TIC  16  where exceeding a discrepancy threshold. 
     To accommodate route requests spanning obstructions, and/or distances greater than the long-range communication capabilities of the communicator  32 , the preferred system  10  further includes a plurality of TIC&#39;s  16 , as shown in  FIG. 7 . The TIC&#39;s  16  are strategically spaced, so as to minimize the number of TIC&#39;s for a given area of coverage. Each TIC  16  is communicatively coupled to and maps separate pluralities of vehicles  12  and links  20 . The TIC&#39;s  16  are communicatively coupled to each other, so that a vehicle  12  can request and receive route and anticipated condition data from other geographic locations. It is appreciated, that this configuration facilitates interstate travel, and can alert an operator at a first location, such as Kansas City, to an anticipated travel time for a link  20  located at a second remote location, such as Detroit. Finally, each receiving vehicle  12  in this configuration is preferably operable to adjustably determine the most proximate TIC  16 . 
     In yet another embodiment, the TIC  16  may be configured to continuously or periodically broadcast the updated map database and anticipated condition values within an operating area. In this configuration, the vehicle  12  is configured to automatically receive at least a portion of the database and anticipated values from the broadcast without request. Again, as previously discussed, where the vehicle  12  further presents a probe vehicle  12   p , an actual condition value can be determined, compared to the anticipated value received, and fed back to the TIC  16  where exceeding a discrepancy threshold, so as to provide feed back data. 
     The preferred forms of the invention described above are to be used as illustration only, and should not be utilized in a limiting sense in interpreting the scope of the present invention. Obvious modifications to the exemplary embodiments and methods of operation, as set forth herein, could be readily made by those skilled in the art without departing from the spirit of the present invention. The inventors hereby state their intent to rely on the Doctrine of Equivalents to determine and assess the reasonably fair scope of the present invention as pertains to any system or method not materially departing from but outside the literal scope of the invention as set forth in the following claims.