Abstract:
The present invention predicts traffic conditions based on traffic information exchanged by means of short range wireless communications, between vehicles moving in an opposite direction. A method in accordance with an embodiment of the present invention includes: successively recording traffic information based on traffic encountered by the vehicle; sending the traffic information to vehicles moving in the opposite direction; receiving traffic information from vehicles moving in the opposite direction; consolidating the traffic information received from the vehicles; and predicting traffic conditions based on the consolidated traffic information.

Description:
FIELD OF THE INVENTION 
     The present invention is directed to security computer systems embarked in vehicles and more particularly to a method, system and computer program based on short range wireless communications for notifying vehicle drivers about abnormal road traffic conditions and situations. 
     BACKGROUND OF THE INVENTION 
     The announcement of abnormal road traffic conditions, such as a traffic jam, an accident, or a sudden traffic speed decrease is very important to limit the number of accidents on the road. On some highways, dedicated systems are in place for detecting some of these conditions, typically traffic jam conditions. These systems rely on different infrastructure means, such as speed sensors, video surveillance equipment, and information boards to announce abnormal traffic conditions. A problem is that such infrastructure means are expensive to deploy and to maintain. Furthermore they cannot react very quickly to sudden conditions, and they cannot react accurately to traffic conditions with a limited impact on the road. 
     SUMMARY OF THE INVENTION 
     The present invention relates to a method executed in a vehicle, for predicting traffic conditions based on traffic information exchanged using short range wireless communications, between vehicles moving in an opposite direction. A method in accordance with an embodiment of the present invention comprises: successively recording traffic information based on traffic encountered by the vehicle; sending the traffic information to vehicles moving in the opposite direction; receiving traffic information from vehicles moving in the opposite direction; consolidating the traffic information received from the vehicles; and predicting traffic conditions based on the consolidated traffic information. 
     The present invention provides numerous advantages, including, but not limited to:
     (A) The present invention does not require any dedicated infrastructure, and can therefore be deployed on any type of road (i.e., not limited to highways and the like).   (B) The present invention can be implemented with affordable means.   (C) The present invention can react very quickly to abnormal traffic situations.   (D) The present invention can react quickly, even for a situation having a limited impact on the road (a single vehicle blocking the traffic lane can be detected).   

     The foregoing, together with other aspects, features, and advantages of this invention can be better appreciated with reference to the following specification, claims and drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other features of this invention will be more readily understood from the following detailed description of the various aspects of the invention taken in conjunction with the accompanying drawings. 
         FIG. 1  shows the general principles of an embodiment of the present invention. 
         FIG. 2  shows how the vehicle traffic information according to an embodiment of the present invention is structured. 
         FIG. 3  shows a scenario involving four vehicles. 
         FIG. 4  describes components of the traffic manager according to an embodiment of the present invention. 
         FIG. 5  is a flow chart of a method carried out by the traffic manager according to an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The following description is presented to enable one or ordinary skill in the art to make and use the invention and is provided in the context of a patent application and its requirements. Various modifications to the embodiment(s) disclosed herein and the generic principles and features described herein will be readily apparent to those skilled in the art. Thus, the present invention is not intended to be limited to the embodiment(s) shown but is to be accorded the widest scope consistent with the principles and features described herein. 
     A proposed solution for solving the previously mentioned problems and others, is based on an embarked device, named a “Traffic Manager” or “TM” for short, which operates according to the following principles. 
     Each TM is equipped with short range wireless communication means allowing exchange information with other vehicles. Such wireless communications means are directive (the beam does not cover 360°) to limit the exchange of information between vehicles moving in opposite directions. The maximum range of such wireless communication means is sufficient to allow two crossing vehicles to send and receive a limited volume data. This is illustrated on the  FIG. 1  where the vehicle A  101  and the vehicle B  102  exchange information on the road  100 . In an embodiment of the present invention, a TM is mounted at the front of each vehicle (respectively shown as  103  and  104  for the vehicles A  101  and B  102 ), and has a beam of 180° (respectively shown as  105  and  106  for the vehicles A  101  and B  102 ), covering the area ahead of the vehicle. 
     Each vehicle A  101  and B  102  knows at any time its current speed, “S”. This information is shared with the respective TM. 
     Each TM generates, when the vehicle is started, a random number that will be used as an identifier, “ID”. Having this random number long enough virtually ensures that this identifier is unique. In an alternate embodiment of the present invention, this identifier can be a fixed unique number associated with each vehicle. Nevertheless this alternative may raise concerns with respect to some national regulations on privacy. 
     Each TM broadcasts at periodic intervals, using short range wireless communication means, vehicle traffic information  200 , “VTI”, structured according to the diagram described in  FIG. 2 :
 
 VTI=ID+S+TB  
 
TB={TRi}
 
 TRi=D+T+S+W  
 
     The VTI  200  is structured as a set of three fields, including an identifier “ID”  201  field, an own speed “S”  202  field, and a traffic book “TB”  203  field. The traffic book “TB”  203  is constituted by a sequence of traffic records “TRi”  210 , each comprising four fields, respectively containing information on distance “D”  211 , time “T”  212 , speed “S”  213 , and weight “W”  214 . 
     Each TM continuously updates the fields within each TR  210 , so that these fields contain accurate information at any point in time. Furthermore, an aging mechanism is run in the TM to cancel any TR  210  holding information considered as being too old. 
     Each TM manages a traffic prediction pattern, or “TPP” for short, which is built on the basis of the VTI information received from crossing vehicles. The purpose of this TPP is to identify any abnormal traffic condition ahead of the vehicle. When such an abnormal traffic condition is identified, the TM warns the driver through audible and/or visible means. Each TPP is constituted by a sequence of TR following the structure specified above. 
     These principles will be better understood by means of a scenario illustrating how the present invention operates. One scenario, shown in  FIG. 3 , involves four vehicles:
         Vehicles  1  and  3  moving from the left to the right; and   Vehicles  2  and  4  moving from the right to the left.       

     The position of the vehicles is determined using a scale ranging from 0 to 72. For each vehicle, the diagram shows the broadcast information in front of the vehicle (that is the VTI  200 , but where the ID  201  is not shown for keeping the diagram easy to read), and the TPP information behind the vehicle. When TR are void, they are shown as holding a “X”. It is assumed that at the beginning of the scenario, all vehicles have not yet crossed any other vehicle, so that their respective VTI and TPP are empty. An obstacle is present at position  39 . 
     Scenario for Vehicle  1   
     At step  1 , the vehicle is at position  31  and moves to the right with a speed of 90 km/h. This vehicle broadcasts a VTI 1 =(ID 1  (not shown on  FIG. 3 ), S 1 =90, TB 1 =void). The time reference is set equal to 0. 
     At step  2 , the vehicle is blocked by an obstacle at position  38 . Its speed S becomes 0 km/h. Time is equal to 7. The vehicle broadcast a new VTI 1 =(ID 1 , S 1 =0, TB 1 =void). 
     At step  3 , the vehicle is still blocked, and broadcasts the same VTI 1  as before. Time is equal to 14. The vehicle receives the VTI issued by vehicle  2 : VTI 2 =(ID 2 , S 2 =90, TB 2 =void). This VTI 2  is processed, so that the vehicle broadcasts a new VTI 1 =(ID 1 , S 1 =0, TB 1 =[D=0, T=0, S=90, W=1]). This TB 1  reflects that a vehicle at a distance  0 , since a time  0  is moving with a speed 90 km/h, based on a single piece of information. 
     At step  4 , the vehicle is still blocked, now on the obstacle in position  39 . Time is equal to 15. The vehicle broadcasts a VTI 1  updated from the previous one: VTI 1 =(ID 1 , S 1 =0, TB 1 =[D=1, T=1, S=90, W=1]). This TB 1  reflects that a vehicle at a distance  1 , since a time  1  is moving with a speed 90 km/h, based on a single piece of information. 
     At step  5 , the vehicle is still blocked. Time is equal to 27. The vehicle broadcasts a an updated VTI 1 : VTI 1 =(ID 1 , S 1 =0, TB 1 =[D=13, T=13, S=90, W=1]). This TB 1  reflects that a vehicle at a distance  13 , since a time  13  is moving with a speed 90 km/h, based on a single piece of information. The vehicle receives the VTI issued by vehicle  4 : VTI 4 =(ID 4 , S 4 =90, TB 4 =void). This VTI 4  is processed, so that the vehicle broadcasts a new VTI 1 =(ID 1 , S 1 =0, TB 1 =[D=13, T=13, S=90, W=1] [D=0, T=0, S=90, W=1]). This TB 1  reflects that a first vehicle at a distance  13 , since a time  13  is moving with a speed 90 km/h, based on a single piece of information, and that a second vehicle at a distance  0 , since a time  0  is moving with a speed 90 km/h, based on a single piece of information. 
     At the following steps, the vehicle remains blocked in position  39  with a speed equal to zero. The vehicle continues to broadcast an updated VTI 1 , by updating the D and T fields of the TR within the TB. As the vehicle has not received any VTI carrying a TB, its TPP remains void. 
     Scenario for Vehicle  2   
     At step  1 , the vehicle is at position  55  and moves to the left with a speed of 90 km/h. It broadcasts a VTI 2 =(ID 2  (not shown on the  FIG. 3 ), S 2 =90, TB 2 =void). The time reference is set equal to 0. 
     At step  2 , the vehicle is at position  48  and moves to the left with a speed of 90 km/h. It broadcasts the same VTI 2 =(ID 2 , S 2 =90, TB 2 =void). The time reference is set equal to 7. 
     At step  3 , the vehicle is at position  39  and moves to the left with a speed of 90 km/h. It broadcasts the same VTI 2 =(ID 2 , S 2 =90, TB 2 =void). The time reference is set equal to 14. The vehicle receives the VTI issued by vehicle  1 : VTI 1 =(ID 1 , S 1 =0, TB 1 =void). This VTI 1  is processed, so that the vehicle broadcasts a new VTI 2 =(ID 2 , S 2 =90, TB 2 =[D=0, T=0, S=0, W=1]). This TB 2  reflects that a vehicle at a distance  0 , since a time  0  is moving with a speed of 0 km/h, based on a single piece of information. 
     At step  4 , the vehicle is still moving forward with the same speed of 90 km/h, now at the position  38 . Time is equal to 15. The vehicle broadcasts a VTI 2  updated from the previous one: VTI 2 =(ID 2 , S 2 =90, TB 2 =[D=1, T=1, S=0, W=1]). This TB 2  reflects that a vehicle at a distance  1 , since a time  1  is stopped with a speed 0 km/h, based on a single piece of information. 
     At step  5 , the vehicle is still moving with a speed of 90 km/h. Time is equal to 27. The vehicle broadcasts a VTI 2  updated from the previous one: VTI 2 =(ID 2 , S 2 =90, TB 2 =[D=13, T=13, S=0, W=1]). This TB 2  reflects that a vehicle at a distance  13 , since a time  13  is stopped with a speed 0 km/h, based on a single piece of information. The vehicle receives the VTI issued by vehicle  3 : VTI 3 =(ID 3 , S 3 =90, TB 4 =void). This VTI 3  is processed, so that the vehicle broadcasts a new VTI 2 =(ID 2 , S 2 =90, TB 2 =[D=13, T=13, S=0, W=1][D=0, T=0, S=90, W=1]). This TB 2  reflects that a first vehicle at a distance  13 , since a time  13  is stopped with a speed of 0 km/h, based on a single piece of information, and that a second vehicle at a distance  0 , since a time  0  is moving with a speed 90 km/h, based on a single piece of information. 
     At the following steps, the vehicle continues to move to the left at a speed of 90 km/h. It continues to broadcast a VTI 2  updated from the previous one, by updating the D and T fields of the TR within the TB. As the vehicle has not received any VTI carrying a TB, its TPP remains void. 
     Scenario for Vehicle  3   
     At step  1 , the vehicle is at position  0  and moves to the right with a speed of 90 km/h. It broadcasts a VTI 3 =(ID 3  (not shown on the  FIG. 3 ), S 3 =90, TB 3 =void). The time reference is set equal to 0. 
     At steps  2 ,  3  and  4 , the vehicle moves at the same speed to positions  7 ,  14 , and  15 . It broadcasts the same VTI 3 =(ID 3 , S 3 =90, TB 3 =void). The time reference becomes 15. 
     At step  5 , the vehicle is still moving with a speed of 90 km/h. Time is equal to 27. The vehicle broadcasts the same VTI 3 =(ID 3 , S 3 =90, TB 3 =void). The vehicle receives the VTI issued by vehicle  2 : VTI 2 =(ID 2 , S 2 =90, TB 2 =[D=13, T=13, S=0, W=1]). This VTI 2  is processed, so that the vehicle broadcasts a new VTI 3 =(ID 3 , S 3 =90, TB 3 =[D=0, T=0, S=90, W=1]). This TB 3  reflects that a vehicle at a distance  0 , since a time  0  is moving with a speed of 90 km/h, based on a single piece of information. Furthermore, as a non void TB 2  has been received, the vehicle update its TPP with the received TB 2 : TPP 3 =[D=13, T=13, S=0, W=1]. This TPP 3  means that at a distance of  13 , since a time  13 , a vehicle running at speed 0 km/h has been detected, based on a single piece of information. This causes a first level of warning to be given to the driver of the vehicle, as a potential danger. 
     At step  6 , the vehicle is still moving to the right with the same speed of 90 km/h, now at the position  26 . Time is equal to 28. The vehicle broadcasts a VTI 3  updated from the previous one: VTI 3 =(ID 3 , S 3 =90, TB 3 =[D=2, T=1, S=90, W=1]). This TB 3  reflects that a vehicle at a distance  2 , since a time  1  is moving at a speed of 90 km/h, based on a single piece of information. Furthermore the TPP fields are updated from their previous values, so that they become: TPP 3 =[D=12, T=14, S=0, W=1]. This TPP 3  means that at a distance of 12, since a time  14 , a vehicle running at speed 0 km/h has been detected, based on a single piece of information. This causes a first level of warning to be given to the driver of the vehicle, as a potential danger. 
     At steps  7  and  8 , the vehicle is still moving to the right with the same speed of 90 km/h, reaching the position  28 . The vehicles continues to broadcast a VTI 3  updated from the previous ones, and to update the TPP 3  updated from the previous ones. 
     At step  9 , the vehicle reaches the position  32  and the time is equal to 34. The VTI 3  has been updated as VTI 3 =(ID 3 , S 3 =90, TB 3 =[D=14, T=7, S=90, W=1]). This TB 3  reflects that a vehicle at a distance  14 , since a time  7  is moving at a speed of 90 km/h, based on a single piece of information. Furthermore the TPP fields are updated from their previous values, so that they become: TPP 3 =[D=7, T=19, S=0, W=1]. This TPP 3  means that at a distance of 7, since a time  19 , a vehicle running at speed 0 km/h has been detected, based on a single piece of information. This causes a first level of warning to be given to the driver of the vehicle, as a potential danger. Then the vehicle receives the VTI issued by vehicle  4 : VTI 4 =(ID 4 , S 4 =90, TB 4 =[D=7, T=7, S=0, W=1]). This VTI 4  is processed, so that the vehicle broadcasts a new VTI 3 =(ID 3 , S 3 =90, TB 3 =[D=14, T=7, S=90, W=1][D=0, T=0, S=90, W=1]). This TB 3  reflects that a first vehicle at a distance  14 , since a time  7  is moving with a speed of 90 km/h, based on a single piece of information, and that a second vehicle at a distance  0 , since a time  0  is moving with a speed of 90 km/h, based on a single piece of information. Furthermore, as a non void TB 4  has been received, the vehicle update its TPP with the received TB 4 : TPP 3 =[D=7, T=7, S=0, W=2]. Here the received TB 4  has confirmed the information previously received in TB 2  as they both specify a danger at the same distance. This TPP 3  means that at a distance of 7, since a time  7 , a vehicle running at speed 0 km/h has been detected, based on two different pieces of information. This causes a second level of warning to be given to the driver of the vehicle, as a high potential danger. 
     At step  10 , the vehicle is still moving to the right with the same speed of 90 km/h, reaching the position  33 . The vehicles continues to broadcast a VTI 3  updated from the previous ones, and to update the TPP 3  updated from the previous ones. The second level of warning is still present, pushing the vehicle driver to brake. 
     Scenario for Vehicle  4   
     At step  1 , the vehicle is at position  68  and moves to the left with a speed of 90 km/h. It broadcasts a VTI 4 =(ID 4  (not shown on the  FIG. 3 ), S 4 =90, TB 4 =void). The time reference is set equal to 0. 
     At steps  2 ,  3  and  4 , the vehicle moves at the same speed to positions  61 ,  52 , and  51 . It broadcasts the same VTI 4 =(ID 4 , S 4 =90, TB 4 =void). The time reference becomes 15. 
     At step  5 , the vehicle is still moving with a speed of 90 km/h. Time is equal to 27. The vehicle broadcasts the same VTI 4 =(ID 4 , S 4 =90, TB 4 =void). The vehicle receives the VTI issued by vehicle  1 : VTI 1 =(ID 1 , S 1 =0, TB 1 =[D=13, T=13, S=90, W=1]). This VTI 1  is processed, so that the vehicle broadcasts a new VTI 4 =(ID 4 , S 4 =90, TB 4 =[D=0, T=0, S=0, W=1]). This TB 4  reflects that a vehicle at a distance  0 , since a time  0  is stopped with a speed of 0 km/h, based on a single piece of information. Furthermore, as a non void TB 1  has been received, the vehicle update its TPP with the received TB 1 : TPP 4 =[D=13, T=13, S=90, W=1]. This TPP 4  means that at a distance of 13, since a time  13 , a vehicle running at speed 90 km/h has been detected, based on a single piece of information. This does not constitute (yet) a danger as this corresponds to a vehicle running ahead at the same speed. 
     At step  6 , the vehicle is still moving to the left with the same speed of 90 km/h, now at the position  38 . Time is equal to 28. The vehicle broadcasts a VTI 4  updated from the previous one: VTI 4 =(ID 4 , S 4 =90, TB 4 =[D=1, T=1, S=0, W=1]). This TB 4  reflects that a vehicle at a distance  1 , since a time  1  is stopped with a speed of 0 km/h, based on a single piece of information. Furthermore the TPP fields are updated from their previous values, so that they become: TPP 4 =[D=13, T=14, S=90, W=1]. This TPP 4  means that at a distance of  13 , since a time  14 , a vehicle running at speed 90 km/h has been detected, based on a single piece of information. This still does not constitute a potential danger. 
     At steps  7  and  8 , the vehicle is still moving to the left with the same speed of 90 km/h, reaching the position  36 . The vehicles continues to broadcast a VTI 4  updated from the previous ones, and to update the TPP 4  updated from the previous ones. 
     At step  9 , the vehicle reaches the position  32  and the time is equal to 34. The VTI 4  has been updated as VTI 4 =(ID 4 , S 4 =90, TB 4 =[D=7, T=7, S=0, W=1]). This TB 4  reflects that a vehicle at a distance  7 , since a time  7  is stopped with a speed of 0 km/h, based on a single piece of information. Furthermore the TPP fields are updated from their previous values, so that they become: TPP 4 =[D=13, T=20, S=90, W=1]. This TPP 4  means that at a distance of 13, since a time  20 , a vehicle running at speed 90 km/h has been detected, based on a single piece of information. This still does not constitute a potential danger. Then the vehicle receives the VTI issued by vehicle  3 : VTI 3 =(ID 3 , S 3 =90, TB 3 =[D=14, T=7, S=90, W=1]). This VTI 3  is processed, so that the vehicle broadcasts a new VTI 4 =(ID 4 , S 4 =90, TB 4 =[D=7, T=7, S=0, W=1][D=0, T=0, S=90, W=1]). This TB 4  reflects that a first vehicle at a distance  7 , since a time  7  is stopped with a speed of 0 km/h, based on a single piece of information, and that a second vehicle at a distance  0 , since a time  0  is moving with a speed of 90 km/h, based on a single piece of information. Furthermore, as a non void TB 3  has been received, the vehicle update its TPP with the received TB 3 : TPP 4 =[D=13, T=7, S=90, W=2]. Here the received TB 3  has confirmed the information previously received in TB 1  as they both specify a vehicle at almost the same distance. This TPP 4  means that at a distance of  13 , since a time  7 , a vehicle running at speed 90 km/h has been detected, based on two different pieces of information. This still does not constitute a potential danger. 
     At step  10 , the vehicle is still moving to the left with the same speed of 90 km/h, reaching the position  31 . The vehicles continues to broadcast a VTI 4  updated from the previous ones, and to update the TPP 4  updated from the previous ones. 
     Alternate Embodiments 
     Without departing from the spirit of the present invention, some enhancements can be proposed along the following points. 
     The structure of the TR  210  can be completed with a new field named “Information” (or “I” for short) where some specific information can be exchanged from a sending TM to a receiver TM. The I field can carry information, thanks to a pre-defined encoding scheme, such as:
     (A) Sudden deceleration of the vehicle. Here this will help discriminating for instance between a vehicle which has stopped at a green light (according to a relatively smooth deceleration), and a vehicle which has suddenly braked to avoid an obstacle on the road.   (B) The sending vehicle has turned on its warning lights, for advertising a danger.   

     The sending vehicle is experiencing some malfunction that have been detected by an embarked logic. 
     Each vehicle can record a “Road Book” (RB for short) as a finite set of TR  210  where information describing the road profile is recorded. By broadcasting this RB along with the VTI, a receiving vehicle may learn the next to come profile of the road, with for instance information related to speed, or even with additional relation related for instance to any curve or hairpin bend. This would just need to extend the definition of associated TR, by introducing for instance a new field related to the wheel orientation. 
     Traffic Manager 
     The traffic manager  400  (TM) is depicted in  FIG. 4 . In an embodiment of the present invention, the TM  400  comprises a radio transponder  401 , a processor  403 , a system bus  408 , a memory  404 , a clock manager  405 , a vehicle interface  406 , and a user interface  407   
     The radio transponder  401 , with its associated antenna  402 , is used for the sending and receiving of VTI. Upon reception of a VTI sent by another vehicle, the radio transponder  401  issues an event “VTI_Received(VTI)”, received by the TM logic running in the processor  403 . 
     The processor  403 , with its embarked logic, handles of the different events received from the TM (received VTI, timer ticks, vehicle information, etc.) according to the proposed invention. The processor  403  interacts with the other components through a system bus  408 . 
     The memory  404  holds the micro-code implementing the proposed invention, as well as the different pieces of information (VTI, TPP, etc.). 
     The clock manager  405  provides a master clock and generates associated timer tick events. Here it is assumed that the clock manager  405  issues at regular time intervals, of duration TI, a “Timer_Click” event, received by the TM logic running in the processor  403 . 
     The vehicle interface  406  is used to retrieve information from the car, namely the current speed. The user interface  407  is used to warn the vehicle driver, should a traffic information being detected. 
     A method followed by the TM  400  corresponds to the logic described in the diagram shown in  FIG. 5 . 
     Event Detection 
     At  501 , the method starts, typically when the whole TM is powered on. At  502 , a random number is first generated, and then assigned as being the identifier ID of the TM. Conventional means are assumed for generating this random number. At  503 , the method enters a waiting state, expecting events to occur. At  504 , an event has been detected. If the event is the reception of a “Timer_Click” from the clock manager  405 , then control is given to  505 . If the event is the reception of a “VTI_Received(VTI)” from the radio transponder  401 , then control is given to  524 . 
     Reception of a “Timer_Click” 
     At  505 , the TM retrieves through the vehicle interface  406 , the vehicle speed and assigns it to the field S  202 . In an embodiment of the present invention, the passed value corresponds to the vehicle average speed since the last interrogation. At  506 , a test is performed to check if the traffic book TB  203  is void. If it is the case, then control is given to  512 ; otherwise control is given to  507 . 
     Traffic Book TB 
     At  507 , the first traffic record TR  210  of the traffic book TB  203  is set as being the current traffic record cTR. At  508 , the current traffic record cTR is updated. First, the distance field D  211  is incremented with the product of the time interval TI by the sum of the vehicle speed S  202  and of the cTR speed field  213 . Second, the time field T  212  is incremented with the time interval TI. At  509 , a test is performed to check if the current traffic record cRT is the last traffic record TR  210  in the traffic book TB  203 . If it is the case, then control is given to  511 ; otherwise control is given to  510 . 
     At  510 , the next traffic record TR  210  following the cRT in the traffic book TB  203 , becomes the new current traffic record cRT. Then control is given to  508 . At  511 , an housekeeping operation is performed within the traffic book TB  203  by removing any traffic record TR  210  with either a distance field D  211  above a fixed threshold TRDmax, or with a time field T  212  above a fixed threshold TRTmax. 
     Traffic Prediction Pattern TPP 
     At  512 , a test is performed to check if the TPP is void. If it is the case, then control is given to  521 ; otherwise control is given to  513 . At  513 , the first traffic record TR  210  of the traffic prediction pattern TPP is set as being the current traffic record cTR. At  514 , the current traffic record cTR is updated. First, the distance field D  211  is incremented with the product of the time interval TI by the difference between the cTR speed field  213  and the vehicle speed S  202 . Second, the time field T  212  is incremented with the time interval TI. 
     At  515 , a test is performed to check if the distance field D  211  is less than a fixed threshold D_alert. If it is the case, then control is given to  517 ; otherwise control is given to  516 . At  516 , a test is performed to check if the distance field D  211  is less than a fixed threshold D_warn. If it is the case, then control is given to  519 ; otherwise control is given to  518 . 
     At  517 , the vehicle driver is alerted through a visible or audible alerting message built by the user interface component  407 . At  518 , a test is performed to check if the current traffic record cRT is the last traffic record TR  210  in the traffic prediction pattern TPP. If it is the case, then control is given to  521 ; otherwise control is given to  520 . 
     At  519 , the vehicle driver is warned through a visible or audible warning message built by the user interface component  407 . Then control is given to  518 . At  520 , the next traffic record TR  210  following the cRT in the traffic prediction pattern TPP, becomes the new current traffic record cRT. Then control is given to  514 . 
     Broadcasting 
     At  521 , an housekeeping operation is performed within the traffic prediction pattern TPP by removing any traffic record TR  210  with either a distance field D  211  above a fixed threshold TPPDmax, or with a time field T  212  above a fixed threshold TPPTmax. At  522 , the VTI  200  is built from the fields ID  201 , S  202  and TB  203 . At  523 , the VTI  200  is broadcast through the radio transponder  401 . Then control is returned back to  503 . 
     Reception of a Vehicle Traffic Information (VTI) 
     At  524 , the speed S  202  field and the traffic book TB  203  field of the VTI received as argument of the VTI_Received(VTI) event are respectively recorded as local variables rVTI.S and rVTI.TB. At  525 , a new traffic record TR  210  is created in the VTI  200  with the distance D  211  field set equal to 0 (zero), the time T  212  field set equal to zero, the speed S  213  field set equal to the local variable rVTI.S, and the weight W  214  field set equal to 1 (one). 
     At  526 , a new traffic record TR  210  is created in the traffic prediction pattern TPP as a copy of any traffic record TR  210  received in the traffic book TB field  203  of the VTI  200 . At  527 , the traffic records TR  210  of the traffic prediction pattern TPP are sorted by their Distance D field  211 . At  528 , the first traffic record TR  210  of the traffic prediction pattern TPP is set as being the current traffic record cTR. At  529 , a test is performed to check if another traffic record TR  210  is present in the traffic prediction pattern TPP. If it is the case, then control is given to  530 ; otherwise control is given to  503 . 
     At  530 , the second traffic record TR  210  of the traffic prediction pattern TPP is set as being the next traffic record nTR. At  531 , a test is performed to check if the difference between the distance fields D  211  of the nTR and cTR traffic records is less than a fixed threshold Dmin. If it is the case, then control is given to  533 ; otherwise control I given to  532 . At  532 , a test is performed to check if another traffic record TR  210  is present in the traffic prediction pattern TPP. If it is the case, then control is given to  535 ; otherwise control is given to  503 . 
     At  533 , the current traffic record cTR is updated. First, the time T  212  field is replaced by the lowest value between the time T  212  fields of the current traffic record cTR and of the next traffic record nTR. Then, the speed S  213  field is replaced by the lowest value between the speed S  213  fields of the current traffic record cTR and of the next traffic record nTR. Finally the weight W  214  field is incremented by one (1). 
     At  534 , the next traffic record nTR is removed from the traffic prediction pattern TPP. Then control is given to  537 . At  535 , the next traffic record nTR becomes the new current traffic record cRT. At  536 , the next traffic record TR  210  following the nRT in the traffic prediction pattern TPP, becomes the new next traffic record nRT. Then control is given to  531 . At  537 , a test is performed to check if another traffic record TR  210  is present in the traffic prediction pattern TPP. If it is the case, then control is given to  536 ; otherwise control is given to  503 . 
     While the invention has been particularly shown and described with reference to a preferred embodiment, it will be understood that various changes in form and detail may be made therein without departing from the spirit, and scope of the invention.