Abstract:
A method for identifying traffic information includes receiving traffic data including a first identifier, information corresponding to a predicted amount of time to traverse a particular link, and information corresponding to a location associated with the particular link, where the first identifier enables a determination of a type of the information that is included within the received traffic data. The method also includes determining a type of information included within the received traffic data based on the first identifier and determining travel time prediction information based on the predicted amount of time included in the received traffic data only if the first identifier enables a determination that the received traffic data includes a prediction related to an amount of time. The method further includes determining location information based on the information that is included in the received traffic data corresponding to the location associated with the particular link and identifying traffic information based on the determined travel time prediction information and the determined location information.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     The present application claims priority from U.S. provisional application Nos. 60/681,971 filed May 18, 2005, which is titled “Traffic information signal and method and apparatus for providing the signal,” and 60/759,963 filed Jan. 19, 2006, which is titled “Traffic information providing method,” the entire contents of which are incorporated herein by reference. The present application also claims priority from Korean application Nos. 10-2005-0089482 filed Sep. 26, 2005, and 10-2006-0022150 filed Mar. 9, 2006, the entire contents of which are incorporated herein by reference. 
     
    
     BACKGROUND  
       [0002]     1. Field  
         [0003]     This disclosure relates to providing traffic information including a prediction of travel time to traverse a link, and using the provided traffic information.  
         [0004]     2. Description of the Related Art  
         [0005]     With the advancement in digital signal processing and communication technologies, radio and TV broadcasts are being digitalized. Digital broadcasting enables provision of various information (e.g., news, stock prices, weather, traffic information, etc) as well as audio and video content  
       SUMMARY  
       [0006]     In one general aspect, a method for identifying traffic information is provided. The method includes receiving traffic data including a first identifier, information corresponding to a predicted amount of time to traverse a particular link, and information corresponding to a location associated with the particular link. The first identifier enables a determination of a type of the information that is included within the received traffic data. The method also includes determining a type of information included within the received traffic data based on the first identifier and determining travel time prediction information based on the predicted amount of time included in the received traffic data only if the first identifier enables a determination that the received traffic data includes a prediction related to an amount of time. The method further includes determining location information based on the information that is included in the received traffic data corresponding to the location associated with the particular link and identifying traffic information based on the determined travel time prediction information and the determined location information.  
         [0007]     Implementations may include one or more additional features. For instance, determining travel time prediction information may include accessing received data reflecting, among other items, results of measurements made with respect to traffic previously traversing the link, and computing a prediction for future travel based on the received data. Determining travel time prediction information may involve accessing information provided within the received traffic data and recognizing that data as the predicted travel time.  
         [0008]     The method may include receiving information corresponding to a message management structure including information corresponding to a generation time of information reflected in the traffic data. The generation time included within the received message management structure may relate to a plurality of message component structures that correspond to more than one of a predicted or current traffic tendency, a predicted or current amount of traffic, a predicted or current speed, or a predicted or current time to traverse a particular link. Each message component structure may further include an identifier specific to the type of information and the first identifier may be an identifier, in a message component structure, specific to the predicted amount of time to traverse the particular link. Information corresponding to a chronological indication associated with the predicted amount of time revealed by the received information may be received. The chronological indication may reflect a particular time of day for which the predicted amount of time corresponds. The chronological indication may be reflected using the universal time coordinated standard.  
         [0009]     The travel time prediction information and the location information may be determined in a single step. The location information may be determined before the travel time prediction information is determined. Receiving traffic data may include decoding the traffic data such that the received traffic data is decoded traffic data. The information corresponding to a predicted amount of time to traverse a particular link may reflect the predicted amount of time.  
         [0010]     In another general aspect, an apparatus for identifying traffic information is provided. The apparatus includes an interface configured to receive traffic data including a first identifier, information corresponding to a predicted amount of time to traverse a particular link, and information corresponding to a location associated with the particular link. The first identifier enables a determination of a type of the information that is included within the received traffic data. The apparatus also includes a processor configured to determine a type of information included within the received traffic data based on the first identifier and dependent upon whether the first identifier enables a determination that the received traffic data includes a prediction related to an amount of time, determining travel time prediction information based on the predicted amount of time included in the received traffic data. The processor is further configured to determine location information based on the information that is included in the received traffic data corresponding to the location corresponding to the particular link and identify traffic information based on the determined travel time prediction information and the determined location information.  
         [0011]     Implementations may include one or more additional features. For instance, the processor may be configured to receive traffic data including information corresponding to a version number of information reflected in the traffic data. The version number is associated with a specific syntax of the data where any one of multiple syntaxes may be used. The processor may also be configured to receive information corresponding to a message management structure including information corresponding to a generation time of information reflected in the traffic data. The processor may be configured to receive information corresponding to a data length of the received data. The processor may be configured to receive the predicted amount of time reflected in seconds. The processor may be further configured to determine the predicted travel time to traverse a particular link only if the first identifier reveals that the traffic data relates to a predicted amount of time to traverse the particular link.  
         [0012]     In yet another general aspect, a traffic information communication device is provided. The device includes a data receiving interface and a processor configured to process information received from the data receiving interface and to determine travel time prediction information based at least in part on the information received. The received information includes a message management container that identifies a number of included message component structures and a generation time associated with the message component structures, and more than one message component structure. The message component structures includes a component identifier that identifies information corresponding to a predicted or current traffic tendency, a predicted or current amount of traffic, a predicted or current speed, or a predicted or current time to traverse a particular link, and a value associated with the component identifier that corresponds to the predicted or current traffic tendency, the predicted or current amount of traffic, the predicted or current speed, or the predicted or current time to traverse a particular link.  
         [0013]     Implementations may include one or more additional features. For instance, in one implementation, for at least one of the message component structures, the component identifier and the value associated with the component identifier may correspond to a predicted or current traffic tendency. For at least one of the message component structures, the component identifier and the value associated with the component identifier may correspond to a predicted or current amount of traffic. For at least one of the message component structures, the component identifier and the value associated with the component identifier may correspond to a predicted or current speed. For at least one of the message component structures, the component identifier and the value associated with the component identifier may correspond to a predicted or current time to traverse a particular link.  
         [0014]     In one implementation of the device, at least one of the message component structures, the component identifier and the value associated with the component identifier correspond to a predicted or current traffic tendency, at least one of the message component structures, the component identifier and the value associated with the component identifier correspond to a predicted or current amount of traffic, for at least one of the message component structures, the component identifier and the value associated with the component identifier correspond to a predicted or current speed, and for at least one of the message component structures, the component identifier and the value associated with the component identifier correspond to a predicted or current time to traverse a particular link.  
         [0015]     The processor may be configured to receive traffic data including information corresponding to a version number of information reflected in the traffic data. The version number is associated with a specific syntax of the data where any one of multiple syntaxes may be used. The processor may be configured to receive information corresponding to a data length of the received data.  
         [0016]     The details of one or more implementations are set forth in the accompanying drawings and the description below. Other features will be apparent from the description and drawings, and from the claims. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0017]     The accompanying drawings illustrate various implementations.  
         [0018]     In the drawings:  
         [0019]      FIG. 1  illustrates a schematic diagram of a network through which traffic information is provided;  
         [0020]      FIG. 2   a  illustrates a syntax of wirelessly transmitted traffic information;  
         [0021]      FIG. 2   b  illustrates a syntax of TPEG-CTT messages;  
         [0022]      FIG. 2   c  shows syntax of formats of components carrying congestion status information;  
         [0023]      FIGS. 2   d  and  2   e  show syntax of a CTT component carrying CTT events and location information, respectively;  
         [0024]      FIG. 2   f  shows syntax of a CTT component carrying additional information of congestion status information;  
         [0025]      FIG. 3   a  illustrates a syntax of the traffic/congestion information included in the CTT event container;  
         [0026]      FIGS. 3   b  through  3   e  illustrate syntaxes of the average link speed, the link travel time, the link delay, and the congestion type included in the status component shown in  FIG. 3   a,  respectively;  
         [0027]      FIG. 4   a  illustrates a syntax of the traffic/congestion prediction information included in the CTT event container;  
         [0028]      FIGS. 4   b  through  4   d  illustrate syntaxes of the predicted average link speed, the predicted link travel time, and the tendency information included in the status component shown in  FIG. 4   a,  respectively;  
         [0029]      FIG. 5   a  illustrates an example of a database storing the history of traffic status at each link for providing the traffic/congestion prediction information;  
         [0030]      FIG. 5   b  illustrates an example of a graphical user interface configured to predict the average speed at a specific link using the database shown in  FIG. 5   a;    
         [0031]      FIG. 6  illustrates a block diagram of a navigation terminal installed in a car for receiving traffic information transmitted from a server in accordance with one implementation;  
         [0032]      FIGS. 7   a  through  7   c  illustrate examples of graphical user interfaces configured to display the average speed at each link; and  
         [0033]      FIG. 8  illustrates an example of a graphical user interface configured to display the average speed predicted for a selected link. 
     
    
     DETAILED DESCRIPTION  
       [0034]     One such use for digital broadcasts is to satisfy an existing demand for traffic information. Proposals that involve the use of digital broadcasts for this purpose contemplate the use of standardized formatting of traffic information to be broadcast. This approach may be used to enable the use of traffic information receiving terminals made by different manufacturers, which each could be configured to detect and interpret traffic information broadcast in the same way.  
         [0035]      FIG. 1  is a schematic diagram of a network through which traffic information is provided. A traffic information providing server  100  in a broadcast station may transmit traffic information collected from various sources (e.g., operator input, or information received from another server or probe cars through a network  101 ) wirelessly so that a traffic information receiving terminal (e.g., navigation system installed in a car  200 ) may receive the traffic information.  
         [0036]     As shown in  FIG. 2   a,  the traffic information wirelessly transmitted from the traffic information providing server  100  may be a sequence of TPEG-CTT (transport protocol expert group-congestion and travel-time Information) messages. A message segment of the sequence, i.e., a TPEG-CTT message, whose syntax is shown in  FIG. 2   b,  may include a message management container  21 , a CTT event container (or Application Event Container)  22 , and TPEG-CTT location container  23 . The TPEG-CTT message may also include different type of containers other than, less than, or in addition to the CTT event container as in the TPEG-CTT message  30 .  
         [0037]     The message management container  21  may be used for managing date and time information. The time information may include message generation time (e.g., a chronological time indication). The message generation time may be included in every TPEG-CTT message when the corresponding message is transmitted. The CTT event container  22  may include congestion and travel time status and predicted congestion and travel time status of links, i.e., road segments. The congestion and travel time status may include average link speed, link travel time, link delay, or congestion type, etc.  
         [0038]     The TPEG-CTT location container  23  may employ various location reference processes. For example, a location reference process using a coordinate system or a location reference process using pre-promised links may be used. When a coordinate system is used, the coordinates (latitudes and longitudes) of the start and end positions of a link for which the TPEG-CTT message is created, may be transmitted. When a reference process using pre-promised links is used, a unique identification for a specific link on a receiving device may be transmitted. For example, a receiving device may include a locally stored network of links, wherein each link may be identified by a unique identifier. A link may refer to a road segment which starts and ends at junctions and has no junction in between. The coordinate system may be the WGS 84 model. A text formatted name of the link may be transmitted.  
         [0039]     In various implementations, a CTT event container and a TPEG-CTT location container, as illustrated in  FIG. 2   c,  are composed of one or more CTT components  201 . Each of CTT components may be constructed according to the syntax shown in  FIG. 2   d  if it carries congestion status information while it may be constructed according to the syntax shown in  FIG. 2   e  if the component carries location information.  
         [0040]     A CTT event container  22  may be composed of one component or a plurality of CTT components. In various implementations, CTT components including an ID of 80 h (notation ‘h’ means hexadecimal) or 84 h includes one or more status components including basic traffic information such as the average link speed, link travel time, link delay, or congestion type. In the description, specific IDs are described as assignments to structures associated with specific information. The actual value of an assigned ID (e.g., 80 h) is exemplary, and different implementations may assign different values for specific associations or circumstances.  
         [0041]     In various implementations, CTT components including an ID of 81 h include one or more status components including predicted CTT status. The predicted CTT status may include predicted average link speed, predicted link travel time, or congestion acceleration tendency. The congestion acceleration tendency may include information indicative of the tendency of congestion status. The congestion acceleration tendency will be described as a type of prediction information as the congestion status in the near future may be predicted from it.  
         [0042]     In various implementations, the TPEG-CTT message may comprise CTT components structured as  FIG. 2   f  to deliver additional information of traffic information. As shown, an identifier  8 Ah may be assigned to the CTT component carrying additional information, and a language code that is indicative of language used for the additional information may also be included in the CTT component.  
         [0043]      FIG. 3   a  shows an example of a syntax of the CTT component included in the CTT event container, which delivers the current congestion and travel time status. The CTT component may be assigned an ID  3   a  including a value of 80 h or 84 h and may include m status components  3   c  and a field  3   b  indicative of the length of the data included in the status components included therein, the length being expressed in the unit of byte. Other units, such as bit, may be used.  
         [0044]     The status components  3   c  may include information on the average link speed, the link travel time, the link delay, and/or the congestion type. The syntax, according to one implementation, of each of which, is shown in  FIGS. 3   b,    3   c,    3   d,  and  3   e,  respectively. In one implementation, status components delivering the average link speed, the link travel time, the link delay, and the congestion type are assigned IDs of ‘00’, ‘01’, ‘02’, and ‘03’, respectively. The link delay may be, for example, the delay in the time required to pass through the link under current traffic condition with respect to the time required to pass through the link at a limit speed specified in the link. The link delay may be expressed in the unit of minute, second, tens or tenths of seconds, or another unit. The link delay may be calculated with respect to the average time required to pass the link on the same days or in the same time slot. The link delay may enable traffic information receiving terminals that do not have information on each link (e.g., speed limit in the link, length of the link, etc) to expect the time required to pass a link.  
         [0045]      FIG. 4   a  shows an example of a syntax of the CTT component included in the CTT event container, which delivers the predicted congestion and travel time status. The CTT component may be assigned an ID  4   a  including a value of 81 h and may include m status components  4   c  and a field  4   b  indicative of the length of the data included in the status components included therein, the length, may be, for example, expressed in the unit of byte.  
         [0046]     The status components  4   c  may include information on the predicted average link speed, the predicted link travel time, and/or, the congestion acceleration tendency, the syntax, according to one implementation, of each of which, is shown in  FIGS. 4   b,    4   c,  and  4   d,  respectively. The status components delivering the predicted average link speed, the predicted link travel time, and the congestion acceleration tendency may be assigned IDs of ‘00’, ‘01’, and ‘02’, respectively.  
         [0047]     Alternatively, the predicted congestion and travel time status may be delivered by the CTT component that delivers the current congestion and travel time status (e.g., average link speed, link travel time, link delay, congestion type) including an ID of 80 h or 84 h. In this case, the status components delivering the predicted congestion and travel time status may be assigned IDs different from the IDs of the status components delivering the current congestion and travel time status.  
         [0048]     The server  100  may create predicted status information shown, according to one implementation, in  FIGS. 4   b  through  4   d  based on the traffic information which may be collected from various sources and/or its own traffic information database, which will be described in detail below.  
         [0049]     To provide predicted traffic information, the server  100  may store the average speed at each link according to day, time slot, week, month, or year. For example, in one implementation, the server  100  may store the average speed at each link at intervals, such as every 30 minutes, as shown in  FIG. 5   a.  The unit of the values shown in  FIG. 5   a  is km/h, though other units, such as m/s, may be used.  
         [0050]     Additionally, in one implementation, the server  100  may store the average speed, or other information, such as travel time or congestion, of links for which the traffic information is currently provided at intervals for a predetermined period of time (e.g., 3 hours) and compare the pattern of change in the average speed for the period of time with the pattern of change in the same time slot of the same day stored in the database. For example, if  FIG. 5   b  shows the pattern of change in the average speed for the past 3 hours from 4:30 pm on a Monday afternoon (A), the server  100  compares the data with the average speeds of from 1:30 pm to 4:30 pm stored in the database (B). If the difference (e.g., the sum of the absolute values of the difference in average speeds at each corresponding time or a weighted sum thereof) is less than a predetermined threshold, the server  100  reads the average speed B 1  at 30 minutes after the current time (i.e., the average speed at 5:00 pm) from the database and transmits the value as the predicted average speed in the corresponding link according to the syntax shown in  FIG. 4   b.  The predicted average link speed may be expressed in the unit of km/h, for example. The predicted time (e.g., 5:00 pm in the previous example) may also be transmitted in the form of the syntax shown in  FIG. 4   b,  for example in UTC (Universal Time Coordinated) format.  
         [0051]     Explaining  FIG. 4   b  in more detail, the predicted time in UTC format may be indicative of a target time or date in the future, and the predicted speed indicates average speed (in km/h, for example) on a link at the target time or date, such as, a day of year, month of year, year, holiday, time of day, rush hour, event, morning/afternoon/evening. For example, the link may be an inter-road between cities, a bridge, or a road between intersections. The data may be incorporated into the component in units of a byte unit, and/or it may be incorporated in units of a bit or a long byte, according to data size. In addition, the speed may be expressed in various units, for example, m/sec, mile/hour, etc.  
         [0052]     In one implementation, if the calculated difference exceeds the predetermined threshold, i.e., it is determined that the pattern of change in the average speed stored in the database does not match the pattern of change in the measured average speed, the server  100  may not provide the predicted average link speed, or alternatively, the server  100  may estimate the predicted average link speed A 1  from the average link speeds extracted for the past 3 hours and provide the estimated value as the predicted average link speed. Various processes may be used to estimate the average speed from the measured average speed values. One process, for example, involves calculation of a weighted sum which gives the latest sample value the highest weight and gives the oldest sample value the lowest weight. For example, the predicted speed A 1  in  FIG. 5   b  can be extracted by calculating 0.5×current speed+0.2×speed of 30 minutes ago+0.1×speed of 1 hour ago+0.1×speed of 1.5 hours ago+0.05×speed of 2 hours ago+0.05×2.5 hours ago, etc.  
         [0053]     After calculating the predicted average link speed in the aforementioned way, the server  100  may calculate the predicted travel time of each link and transmit the predicted travel time of each link along with associated predicted time according to the syntax shown in  FIG. 4   c.  The predicted travel time may be calculated by multiplying the predicted average speed at each link by the length of the corresponding link stored in the database. The predicted travel time may be expressed in the unit of minutes, tens of seconds, second, or a unit smaller than seconds, for example.  
         [0054]     When providing the average speed in a particular link, the server  100  may compare the current average speed with the average speed at the previous time slot and provide the tendency of change in the average link speeds  41  according to the syntax shown in  FIG. 4   d.  In one implementation, the information, which is called the congestion acceleration tendency, may have one value among several values defined by a table shown in  FIG. 4   d.  For example, the information may be assigned 1 if the current average speed is higher than the average speed of 30 minutes ago. The congestion acceleration tendency may be assigned 2 if the current average speed is lower than the average speed of 30 minutes ago. The congestion acceleration tendency may be assigned 3 if the average speed remains unchanged. If there is no available data to compare, the congestion acceleration tendency may be assigned 0. The congestion acceleration tendency information may enable a driver to choose a route that shows improvement in the traffic congestion from among several possible routes showing similar average speeds. Instead of providing the congestion acceleration tendency in the form of a number (e.g., 1, 2, 3, etc.), the server  100  may provide the rate of change of the average speed, i.e., the slope in the graph shown in  FIG. 5   b  as the congestion acceleration tendency, or other indicia or descriptors.  
         [0055]     In one implementation, the server  100  may prevent the size of information which it should transmit from becoming excessively large by maintaining the ratio of the current congestion and travel time status to the predicted congestion and travel time status below an appropriate level (e.g., 3:1).  
         [0056]      FIG. 6  is an example of a block diagram of a navigation terminal for receiving traffic information transmitted from the server  100 .  FIGS. 6-8  are example implementations of systems for receiving and utilizing traffic information, and interfaces used to output information generated by such systems. Other systems may be organized differently or include different components.  
         [0057]     As illustrated by  FIG. 6 , the navigation terminal comprises a tuner  1  for receiving modulated traffic information signals by resonating at the required frequency band, a demodulator  2  for outputting traffic information signals by demodulating the modulated signals from the tuner  1 , a TPEG-CTT decoder  3  for extracting traffic information by decoding the demodulated traffic information signals, a GPS module  8  for calculating the current position (i.e., latitude, longitude, and altitude) by receiving signals from a plurality of low-orbit satellites, storage structure  4  for storing various graphic data and an electronic map including information on links and nodes, an input device  9  for receiving user input, a navigation engine  5  for controlling screen display based on the user input, the current position, and extracted traffic information, a memory  5   a  for storing data temporarily, an LCD panel  7  for displaying data, and an LCD drive  6  for driving the LCD panel  7  according to data to be presented. The input unit  9  may be a touch screen incorporated into the LCD panel  7 .  
         [0058]     The tuner  1  tunes to the frequency of the signals transmitted by the server  100  and the demodulator  2  demodulates the tuned signals in a predetermined manner. The TPEG-CTT decoder  3  decodes the demodulated signals into a TPEG-CTT message sequence as shown in  FIG. 2 , interprets each TPEG message included in the TPEG-CTT message sequence, and sends necessary information and/or control signals to the navigation engine  5 . For purposes of brevity, the following description focuses on basic congestion and travel time status shown in  FIGS. 3   b  through  3   e  and predicted congestion and travel time status shown in  FIGS. 4   b  through  4   d  though other status information is involved, such as, for example, speed, is involved.  
         [0059]     The TPEG-CTT decoder  3  extracts date/time and message generation time included in the message management container of each TPEG message and determines if the following container is a CTT event container based on ‘message element’ information (i.e. an identifier). If it is determined that the following container is a CTT event container, the TPEG-CTT decoder  3  provides the navigation engine  5  with the information extracted from the CTT component included in the CTT event container so that the navigation engine  5  may display congestion and travel time status and predicted congestion and travel time status, which will be described below. Providing the navigation engine  5  with the information may include determining, based on identifiers, that the traffic information includes a message management container including status information within various message components within the message management container. The components may each include different status information associated with different links or locations and identifiers associated with the different status information. The containers and components may each include information associated with a generation time, version number, data length, and identifiers of included information.  
         [0060]     The TPEG-CTT decoder  3  then extracts information on the link location for which the previously extracted information is intended from the following TPEG-CTT location container. The position information may be, for example, the coordinates (i.e., latitudes and longitudes) of the start and end positions or an ID that is uniquely assigned to each link, depending on the type of the TPEG-CTT location container. If the navigation terminal is equipped with the storage structure  4 , the navigation engine  5  finds the location of the link for which the received traffic information is intended with reference to the information on each link and node stored in the storage structure  4 . The navigation engine  5  may convert the coordinates of a link into a link ID or vice versa.  
         [0061]     The navigation engine  5  reads a part of the electronic map centered around the position coordinates received from the GPS module  8  from the storage structure  4  and displays the map on the LCD panel  7  via the LCD drive  6 . A particular graphic symbol is displayed at the location corresponding to the current position on the LCD panel  7 .  
         [0062]     The navigation engine  5  displays the average link speed received from the TPEG-CTT decoder  3  at a location corresponding to the coordinates or link ID delivered via the TPEG-CTT location container following the container delivering the average link speed. There are various processes for the navigation engine  5  to display the traffic information. For example, the navigation engine  5  may show links in different colors according to the average speed at the links as shown in  FIGS. 7   a  and  7   b,  where the colors red, orange, green, and blue (colors themselves not shown) may be used to indicate average speeds of 0˜10 km, 10˜20 km, 20˜40 km, over 40 km, respectively. Alternatively, the navigation engine  5  may show the average link speed in numbers at each link as shown in  FIG. 7   c,  or a combination of colors and numbers may be used. In addition or as an alternative, the navigation engine  5  may use similar display tools to display the congestion acceleration tendency received from the TPEG-CTT decoder  3  at the corresponding link, or through the use of other display tools such as through the use of an icon or a string (e.g., ‘improved’ if the value of the congestion acceleration tendency is 1 and ‘deteriorated’ if the value is 2). In this case, the navigation engine  5  maintains the status unchanged if the value of the congestion acceleration tendency is 0 or 3. If the congestion acceleration tendency is received in the form of the rate of change of the average speed, the navigation engine  5  displays the value only when a request from the user is received to prevent visual confusion of the user. The rate of change may be displayed together for a user-chosen route or a front link.  
         [0063]     If the navigation terminal is not equipped with the storage structure  4  for storing an electronic map, the terminal may show the average link speed at links located in front of the current position in different colors, as shown in  FIG. 7   b,  or in numbers, as shown in  FIG. 7   c.  If the route of the vehicle with the navigation terminal installed is determined, the navigation terminal may show the average speed at the links included in the determined route instead of the links located in front of the current position.  
         [0064]     The navigation engine  5 , responsive to user input, may display the link travel time, the link delay, and the congestion type received from the TPEG-CTT decoder  3  on the LCD panel  7  instead of or simultaneously with the average link speed.  
         [0065]     If the user requests predicted congestion and travel time status through the input unit  9 , the navigation engine  5  displays the predicted average link speed at each link received from the TPEG-CTT decoder  3  in colors or in numbers instead of the current average link speed. In this case, the colors or numbers describing the predicted status may be displayed simultaneously with the current average link speed but the location or used colors may be different. If the user switches the display mode to see the predicted link travel time instead of the predicted average link speed, the navigation engine  5  displays the predicted link travel time on the electronic map or graphics on the LCD panel  7 .  
         [0066]     If the navigation engine  5  is capable of routing, the navigation engine  5  may search or research the desirable route based on the received predicted average link speed or predicted link travel time. For example, the navigation engine  5  finds the shortest time path to the destination by using the predicted link average time or predicted link travel time at each link to be reached 30 minutes later at the current speed.  
         [0067]     If the terminal in  FIG. 6  is equipped with a voice output capability, the terminal may audibly output the received predicted status or congestion tendency information for a specified link or links.  
         [0068]     The information and/or control signals received from the TPEG-CTT decoder  3  are temporarily stored in the rewritable memory  5   a  and used by the navigation engine  5 . After using the information stored in the memory  5   a,  the navigation engine  5  may store the average link speed or link travel time at intervals of, such as, for example, 20 minutes (e.g., 1:00, 1:20, 1:40) for the last 1 hour. The interval of storage may differ depending on the storage capacity of the memory  5   a.  By automatically expiring the information from within memory, the system may be assured that it is working with recent information when consulting the contents of the memory, and thus may be able to represent information as current with confidence without having to otherwise maintain or check information reflecting when the stored data was collected/aggregated/stored.  
         [0069]     If a specific link is selected by the user while the average speed at each link is stored in the memory  5   a,  the navigation engine  5  controls the LCD drive  6  so that the history of the average link speed or the history of the link travel time at the specified link is displayed as a graph shown in  FIG. 8 . In the graph, the unit of the displayed numbers is km/h and the name  81  of the link is displayed on the graph. The link name is received along with the coordinates of the link or link ID through the TPEG location container  23  or included in the electronic map stored in the storage structure  4 . The current congestion status, predicted congestion status, or other status may be displayed in other or different ways.  
         [0070]     If the predicted congestion status is not included in the received traffic information, the navigation engine  5  may predict the average speed using the current average speed and the history of the average link speed stored in the memory  5   a  and display the predicted average link speed, as shown in  FIG. 8   a.  The method for predicting the average link speed may be the same as the aforementioned prediction method executed in the server  100 .  
         [0071]     While the disclosure has discussed a limited number of implementations, those skilled in the art having the benefit of this disclosure will appreciate numerous modifications and variations therefrom. It is intended that all such modifications and variations fall within the spirit and scope of this disclosure.