Patent Publication Number: US-2010112529-A1

Title: Safe driving evaluation system and safe driving evaluation program

Description:
INCORPORATED BY REFERENCE 
     The disclosure of Japanese Patent Application No. 2008-280371 filed on Oct. 30, 2008 including the specification, drawings and abstract is incorporated herein by reference in its entirety. 
     BACKGROUND OF THE INVENTION 
     The present invention relates to a safe driving evaluation system and a safe driving evaluation program which are based on a sudden braking percentage. 
     DESCRIPTION OF THE RELATED ART 
     There are conventional systems that evaluate vehicle driving based on the frequency of sudden braking. For example, Japanese Patent Application Publication No. JP-A-2008-77502 describes art that evaluates a safe driving degree, which indicates how safe a driver is driving based on the frequency of sudden starts and sudden braking per unit time. Japanese Patent Application Publication No. JP-A-2005-7932 also describes art that calculates a sudden braking frequency as the number of times sudden braking occurs per predetermined period, or as a ratio of the number of times sudden braking occurs to the total number of braking operations. Comments are then provided to the driver to encourage more appropriate braking if the sudden braking frequency is higher than a standard frequency. 
     SUMMARY OF THE INVENTION 
     However, sudden braking in the systems described in JP-A-2008-77502 and JP-A-2005-7932 are all treated the same as one sudden braking operation. Therefore, if the art described in JP-A-2008-77502 or JP-A-2005-7932 is used for a safe driving evaluation, the results of the safe driving evaluation may lack validity. Namely on roads with smooth traffic flows, there is little need for braking as long as there is no congestion. If sudden braking occurs, it would likely have a large effect on a following vehicle. However, the sudden braking in this case is treated the same as any other sudden braking. Therefore, although the above systems can suppress the overall frequency with which sudden braking occurs, the safe driving evaluations do not give any consideration to the effect the sudden braking may have on a following vehicle. 
     The present invention was devised in light of the foregoing problem, and provides a safe driving evaluation system and a safe driving evaluation program that perform a safe driving evaluation based on a sudden braking percentage, which considers the necessity of braking at a location where sudden braking occurred, in order to increase a driver&#39;s awareness to refrain from sudden braking, particularly on a road where the necessity for sudden braking is considered small. 
     In order to achieve the above object, a safe driving evaluation system according to a first aspect of the present invention includes: a counting unit that counts a frequency of a braking operation of a vehicle; a determination unit that determines whether the braking operation is a sudden braking operation; a percentage calculation unit that calculates a sudden braking percentage as a ratio of a sudden braking operation frequency, which is the number of times the braking operation is determined as a sudden braking operation by the determination unit, to the braking operation frequency counted by the counting unit; a correction unit that determines when sudden braking occurs whether a vehicle deceleration frequency is low for a road where the sudden braking occurred, and corrects the sudden braking percentage to a higher value if the vehicle deceleration frequency is determined as low; and an evaluation information acquisition unit that acquires evaluation information based on the sudden braking percentage. 
     According to the above constitution, the sudden braking percentage is calculated as a ratio of the sudden braking operation frequency to the braking operation frequency. However, the sudden braking percentage may be corrected to a higher value if the sudden braking occurred on a road that normally has a smooth traffic flow, such as an expressway or a bypass road, where the necessity for braking is considered small. Therefore, a sudden braking percentage can be obtained that gives consideration to the effect of the sudden braking on a following vehicle. Because the evaluation information is acquired based on the sudden braking percentage, the driver can objectively find out an overall trend regarding how safely he or she is driving in terms of braking based on the evaluation information. It is thus possible to increase the driver&#39;s awareness of safe driving in terms of braking, and increase the driver&#39;s awareness of refraining from sudden braking on roads with a low vehicle deceleration frequency where the necessity of sudden braking is considered small. 
     The safe driving evaluation system may further include a brake assist detection unit that detects an operation signal of a brake assist device of the vehicle, wherein the determination unit determines whether the braking operation is a sudden braking operation based on the operation signal. 
     In a vehicle that includes a brake assist device, if the speed or strength with which the driver depresses the brake pedal is greater than that during normal braking, a brake assist operation is performed that amplifies the braking effect with respect to the driver&#39;s brake depression force. According to this constitution, an existing component can be utilized without providing a special component to easily determine when braking occurs whether the braking operation is a sudden braking operation. 
     The safe driving evaluation system may further include an acceleration information acquisition unit that acquires information indicating an acceleration of the vehicle, wherein the determination unit determines whether the braking operation is a sudden braking operation based on a deceleration detected by the acceleration information acquisition unit. 
     Sudden braking generates a large deceleration of the vehicle, and therefore, adopting the above constitution enables suitable determination when braking occurs regarding whether the braking operation is a sudden braking operation. 
     In addition, the correction unit may determine whether the vehicle deceleration frequency is low for a road where sudden braking occurred based on either or both the number of traffic signals and intersections present within a prescribed deceleration frequency determination zone, which is set using a point where the sudden braking occurred as a reference point. 
     Roads provided with few traffic signals and intersections can generally be considered roads where the necessity of braking is small. Hence, according to this constitution, such a general road trend can be utilized to easily determine whether the vehicle deceleration frequency for a road is low. Because the determination is based on the number of traffic signals and intersections within a prescribed zone that is set using the point where sudden braking occurred as a reference point, the surrounding conditions of the host vehicle can be suitably reflected in the determination result. 
     The deceleration frequency determination zone may also be set such that a zone ahead of the point where sudden braking occurred is larger than a zone behind the point. 
     The vehicle deceleration frequency serves as a reference regarding whether the necessity of sudden braking is small. This necessity is greatly affected by the number of traffic signals and intersections present ahead of the vehicle. Therefore, the area in front of the vehicle should be emphasized more than the area behind the vehicle. Hence, adopting the above constitution enables suitable establishment of the deceleration frequency determination zone. 
     By including the zone rearward of the point where sudden braking occurred, the actual current location of the vehicle can be included in the deceleration frequency determination zone even if current location information for the vehicle in the safe driving evaluation system has a margin of error in front and back of the actual current location along the traveling direction of the vehicle. Therefore, regardless of whether there is a margin of error as described above, the determination regarding whether the vehicle deceleration frequency is low can be suitably made. 
     The safe driving evaluation system may further include map data that is referable and includes information regarding a location where either or both a traffic signal and an intersection exist, wherein the correction unit acquires either or both the number of traffic signals and intersections from the map data. 
     According to this constitution, the number of traffic signals and intersections on the road where sudden braking occurred can be easily acquired. 
     The safe driving evaluation system may further include referable map data that includes road type information representing types of roads, wherein the correction unit determines whether the vehicle deceleration frequency is low for a road where the sudden braking occurred based on the road type information acquired from the map data. 
     The road type is generally related to the necessity for braking due to the existence of a traffic signals and intersections. For example, a road indicated as an expressway in the road type information can be considered as having a low vehicle deceleration frequency. According to this constitution, it is possible to determine with a simple configuration whether the vehicle deceleration frequency is low for a road where sudden braking occurred. 
     The evaluation information acquisition unit may acquire as the evaluation information at least one of points assigned depending on the sudden braking percentage, advice whose content depends on the sudden braking percentage, and a graph display that visually represents the sudden braking percentage at certain times. 
     According to this constitution, the content of the evaluation according to the sudden braking percentage can be suitably communicated to the driver. 
     The safe driving evaluation system may further include an information collection unit that collects information regarding the sudden braking percentage from a plurality of vehicles, wherein the evaluation information acquisition unit acquires as the evaluation information either or both a ranking for each vehicle regarding the sudden braking percentage as compared to the other vehicles and a level assigned based on the past sudden braking percentages of each vehicle compared to the other vehicles. 
     According to this constitution, when the information regarding the sudden braking percentage is collected from a plurality of vehicles, the content of the evaluation information can be used as evaluation content that is based on a comparison with other vehicles. Therefore, the content of the evaluation according to the sudden braking percentage can be more suitably communicated to the driver. 
     The safe driving evaluation system may further include an on-vehicle terminal device installed in the vehicle; and a central control device provided in communication with a plurality of the on-vehicle terminal devices, wherein when a main power source of the vehicle installed with the on-vehicle terminal device is turned off, the on-vehicle terminal device sends information regarding the sudden braking percentage between turning the main power source on and off to the central control device, and the central control device generates the evaluation information for the on-vehicle terminal device based on the information regarding the sudden braking percentage received from the on-vehicle terminal device. 
     According to this constitution, information regarding the sudden braking percentage is collected in the central control device from the on-vehicle terminal devices respectively installed in the plurality of vehicles. Based on the information regarding the sudden braking percentages for the plurality of vehicles, the evaluation information for each on-vehicle terminal device can be generated. Accordingly, evaluation information with suitable content based on a comparison of the plurality of vehicles can be provided to each on-vehicle terminal device. In addition, when the main power source of the vehicle installed with the on-vehicle terminal device is turned off, information regarding the sudden braking percentage between turning the main power source on and off is sent to the central control device. Therefore, it is possible to collect the information regarding the sudden braking percentage while the main power source of the vehicle is turned on in the central control device with a small number of communications. Consequently, much information can be efficiently collected in the central control device so that more suitable evaluation information can be provided to each on-vehicle terminal device. 
     The technical constitution of the safe driving evaluation system according to the first aspect of the present invention, having the respective constitutions described above, may be applied to a safe driving evaluation method and a safe driving evaluation program, and therefore, the present invention also claims rights as this type of method and program. 
     A safe driving evaluation program in such case performs in a computer the functions of: counting a frequency of a braking operation of a vehicle; determining whether the braking operation is a sudden braking operation; calculating a sudden braking percentage as a ratio of a sudden braking operation frequency, which is the number of times the braking operation is determined as a sudden braking operation by the determination unit, to the braking operation frequency counted by the counting unit; determining when sudden braking occurs whether a vehicle deceleration frequency is low for a road where the sudden braking occurred, and corrects the sudden braking percentage to a higher value if the vehicle deceleration frequency is determined as low; and acquiring evaluation information based on the sudden braking percentage. 
     Needless to say, this safe driving evaluation program is also capable of obtaining the actions and effects of the safe driving evaluation system described above, and moreover, the several techniques cited as preferred constitutional examples thereof may be incorporated therein. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram that shows an overall configuration of a navigation device according to an embodiment of the present invention; 
         FIG. 2  is a block diagram that shows an overall configuration of a central control server according to the embodiment of the present invention; 
         FIG. 3  is a drawing that shows an example of a total evaluation screen that displays evaluation information acquired by an evaluation information acquisition unit; 
         FIG. 4  is a drawing that shows an example of a guidance screen that displays evaluation graph information for sequentially showing changes in a sudden braking percentage during travel; 
         FIG. 5  is a flowchart that shows an overall procedure for a safe driving evaluation process according to the embodiment of the present invention; and 
         FIG. 6  is a flowchart showing a procedure of sudden braking percentage calculation processing. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Embodiments of the present invention will be described now with reference to the drawings. The description here regards an example in which the safe driving evaluation system according to the present invention includes an on-vehicle navigation device  1  and a central control server  2  that is provided in communication with a plurality of navigation devices  1 .  FIG. 1  is a block diagram that shows an overall configuration of the navigation device  1 . The navigation device  1  that forms the safe driving evaluation system counts the number of times a braking operation of a vehicle  3  is performed (a braking frequency), and determines whether the braking operation is a sudden braking operation. When calculating a sudden braking percentage that is a ratio of a sudden braking frequency to the braking frequency, the sudden braking percentage is corrected to a higher value if the sudden braking occurred on a road where the necessity for braking is considered small. Based on the sudden braking percentage, evaluation information  61  (see  FIGS. 3 and 4 ) is acquired and output. In the evaluation information  61 , a lower sudden braking percentage results in a better evaluation. Accordingly, the driver of the vehicle  3  installed with the navigation device  1  can objectively find out an overall trend regarding how safely he or she is driving in terms of braking based on the evaluation information  61 . It is thus possible to increase the driver&#39;s awareness of safe driving in terms of braking, and increase the driver&#39;s awareness of refraining from sudden braking on roads where the necessity of sudden braking is considered small. 
       FIG. 2  is a block diagram that shows an overall configuration of the central control server  2 . The central control server  2  collects and sums information from the plurality of navigation devices  1  that are respectively installed in a plurality of vehicles  3 . The central control server  2  then generates the evaluation information  61  from the collected information and distributes the evaluation information  61  to the navigation devices  1 . In the present embodiment, the navigation device  1  corresponds to an on-vehicle terminal device of the present invention, and the central control server  2  corresponds to a central control device and an information collection unit of the present invention. 
     1. Configuration of Navigation Device 
     The configuration of the navigation device  1  will now be described. The components of the navigation device  1  shown in  FIG. 1  each have as its core member a computation processing device such as a CPU or the like that is one of mutually shared and independently utilized. Each component executes various processes on received data that may be implemented by hardware, software (a program), or via a combination of both hardware and software. In the present embodiment, the navigation device  1  includes a transmitter-receiver unit  11 ; a host vehicle position acquisition unit  12 ; a navigation computation unit  13 ; a notification processing unit  16 ; a main power source monitoring unit  28 ; a send processing unit  29 ; an update processing unit  30 ; a vehicle deceleration frequency determination unit  14 ; a brake signal detection unit; a brake assist signal detection unit  17 ; a brake counting unit  18 ; a sudden braking determination unit  19 ; a percentage calculation unit  22 ; and an evaluation information acquisition unit  23 . Each component is also configured to exchange information with the other components via wireless communication using a digital transfer bus or the like. If each component is implemented through software (a program), the software is stored in a storage unit such as a RAM or ROM to which the computation processing device can refer. A map database  31  has a hardware configuration that includes a storage medium (a storage unit) such as a hard disk drive, a flash memory, a DVD drive equipped with a DVD-ROM, or a CD drive equipped with a CD-ROM, for example. A memory  32  also has a hardware configuration that includes a storage medium that is capable of storing and re-writing information, such as a hard disk drive or a flash memory. In addition, the memory  32  may be provided in a storage medium shared with the map database  31  if the map database  31  is configured by a re-writable storage medium. The configuration of each component of the navigation device  1  according to the present embodiment will be explained in detail below. 
     1-1. Map Database 
     The map database  31  is a database in which map data  34  is stored. Further, the map data  34  includes road network data constituted by a plurality of nodes that represent a plurality of intersections, and a plurality of links connecting the nodes that represent roads. Each link includes information such as road type, area type, link length, road width, and shape interpolation points for expressing link shapes as link attribute information. Here, the road type information is road classification information used when compartmentalizing roads into a plurality of types such as expressways, motorways, local roads, narrow city streets, and mountain roads. In addition to the road network data, the map data  34  includes rendering information required in map display processing and various types of guidance information required in route guidance processing, which are performed by the navigation computation unit  13 . Here, the rendering information includes information such as background information required to display road shapes, buildings, rivers and so on, character information required to display city, town and village names, road names, and so on. In addition to this, the map data  34  stored in the map database  31  includes information that indicates the positions of points installed with traffic signals (referred to as signal installation points below). The information that indicates the positions of signal installation points can be stored as additional information for nodes that represent intersections installed with traffic signals (e.g. as a flag that indicates whether there is a traffic signal), or stored as attribute information for links that are connected to such nodes (e.g. information that indicates a traffic signal on one link end). 
     1-2. Transmitter-Receiver Unit 
     The transmitter-receiver unit  11  includes a communication device that sends data to the central control server  2  and receives data from the central control server  2  by wireless communication via a wireless base station or the like. A conventional communication network such as a cellular telephone network or a wireless LAN (Local Area Network), for example, may be used as a wireless communication method. In the present embodiment, the transmitter-receiver unit  11  sends information regarding the sudden braking percentage to the central control server  2 , as will be explained later. In addition, the transmitter-receiver unit  11  receives the evaluation information  61  (see  FIGS. 3 and 4 ) that is based on a comparison with other vehicles  3 , such as ranking information  65  and level information  66 , from the central control server  2 . The transmitter-receiver unit  11  also receives update information for updating advice data  37 , point rules  38 , and correction rules  40  stored in the memory  32 . These will be described in more detail later. 
     1-3. Host Vehicle Position Information Acquisition Unit 
     The host vehicle position information acquisition unit  12  acquires host vehicle position information that indicates the current position of the host vehicle. The host vehicle position information acquisition unit  12  is connected to a Global Positioning System (GPS) receiver  41 , a direction sensor  42 , and a distance sensor  43 . Here, the GPS receiver  41  is a device that receives a GPS signal from a GPS satellite. The GPS signal is normally received every second and output to the host vehicle position information acquisition unit  12 . In the host vehicle position information acquisition unit  12 , the signal received by the GPS receiver  41  from the GPS satellite may be analyzed, and additional information may be acquired, such as the current position (coordinates) of the vehicle, the direction in which the vehicle is heading, the vehicle speed, and the like. The direction sensor  42  detects the direction in which the host vehicle is heading and changes in the heading of the host vehicle. The direction sensor  42  may be a gyroscope, a geomagnetic sensor, or the like, for example. Also, the direction sensor  42  outputs the detected heading of the host vehicle to the host vehicle position information acquisition unit  12 . The distance sensor  43  detects the speed of the host vehicle and the distance traveled. The distance sensor  43  may be configured as a vehicle speed pulse sensor that outputs a pulse signal every time a drive shaft, wheel, or the like of the vehicle rotates a certain amount, a yaw sensor and a G sensor that detect an acceleration of the host vehicle, and a circuit that integrates the detected acceleration, for example. Also, the distance sensor  43  outputs information regarding the detected vehicle speed and the detected distance traveled to the host vehicle position information acquisition unit  12 . 
     Based on the outputs from the GPS receiver  41 , the direction sensor  42 , and the distance sensor  43 , the host vehicle position information acquisition unit  12  performs a computation to determine the host vehicle position using conventional methods. In addition, the host vehicle position information acquisition unit  12  executes a correction to match the host vehicle position with a road in the map data  34  by executing a conventional map matching process based on the map data  34  stored in the map database  31 . The host vehicle position information corrected by the map matching process is reflected in the host vehicle position information. Thus the host vehicle position information acquisition unit  12  acquires the host vehicle position information that includes the current host vehicle position indicated by the coordinates (longitude and latitude) and information on the current vehicle heading. 
     1-4. Navigation Computation Unit 
     The navigation computation unit  13  is a computation processing unit that operates in accordance with an application program in order to execute navigation functions such as displaying the host vehicle position, calculating a route from a departure point to a destination, providing guidance for a route to the destination, and searching for a destination. For example, the navigation computation unit  13  acquires the map data  34  around the host vehicle from the map database  31  to display a map image on a display input device  47 , and also executes a process to display a host vehicle position mark superimposed over the map image based on the host vehicle position information. Additionally, the navigation computation unit  13  provides route guidance using either or both the display input device  47  and an audio output device  48 , based on the host vehicle position information and a route calculated using a conventional method from the departure point to the destination. The display input device  47  outputs the evaluation information  61  received from the evaluation information acquisition unit  23  (to be explained in more detail later). Note that in addition to the above, the navigation computation unit  13  is connected to various types of conventional components that are required for the navigation device  1 , such as a remote controller and a user interface that may be a touch panel integrally provided with the display input device  47 . 
     1-5. Brake Counting Unit 
     The brake counting unit  18  functions as a counting unit that counts the number of braking operations of the vehicle  3 . In the present embodiment, when the vehicle  3  brakes, a brake signal is input to the brake signal detection unit  15  while the braking is performed. Based on the detection result of the brake signal detection unit  15 , the brake counting unit  18  updates the braking frequency by adding 1 to the braking frequency each time braking is performed. Note that information pertaining to the braking frequency is stored in the memory  32  in a form that can be referenced and updated by the brake counting unit  18 . 
     Further note that there may be variation in the brake operation amount during braking. However, the time from detection of the brake signal by the brake signal detection unit  15  until non-detection of the brake signal is counted by the brake counting unit  18  as one braking operation. 
     1-6. Sudden Braking Determination Unit 
     The sudden braking determination unit  19  functions as a determination unit that determines whether the braking operation is a sudden braking operation. In the present embodiment, the vehicle  3  includes a brake assist device. If the speed or strength with which the driver depresses the brake pedal is greater than that during normal braking, a brake assist operation is performed that amplifies the braking effect with respect to the driver&#39;s brake depression force. When the brake assist operation is executed, a brake assist signal is input to the brake assist signal detection unit  17 . 
     The brake assist operation is generally performed during sudden braking, and therefore, the sudden braking determination unit  19  determines whether the braking operation is a sudden braking operation based on the detection result of the brake assist signal detection unit  17 . If it is determined that the braking operation is a sudden braking operation, the sudden braking determination unit  19  outputs such information to the percentage calculation unit  22  to be described later. 
     In addition, if the sudden braking determination unit  19  determines that sudden braking has occurred, such information may be output to the notification processing unit  16 . The driver may then be cautioned using characters or icons displayed via the display input device  47 , or using sounds output via the audio output device  48 . 
     1-7. Vehicle Deceleration Frequency Determination Unit 
     The vehicle deceleration frequency determination unit  14  is a component that determines whether a vehicle deceleration frequency is low for a road where sudden braking occurred. In the present embodiment, when information pertaining to the location of a point of sudden braking is input from the percentage calculation unit  22 , such input information is used to determine whether the vehicle deceleration frequency is low for a road where sudden braking occurred. The determination result is then output to the percentage calculation unit  22 . 
     In the present embodiment, the vehicle deceleration frequency determination unit  14  determines whether the vehicle deceleration frequency is low for a road where sudden braking occurred based on the number of traffic signals present within a prescribed deceleration frequency determination zone, which is set using the point where sudden braking occurred as a reference point. For example, if there are five or fewer traffic signals within the prescribed deceleration frequency determination zone, the vehicle deceleration frequency may be determined as low. Note that the number five is merely an example, and may be changed as appropriate. Instead of the number of traffic signals, the determination may be made using the number of intersections, or the vehicle deceleration frequency may be determined based on both the number of traffic signals and intersections. 
     Note that in the present embodiment, the vehicle deceleration frequency determination unit  14  can refer to the map data  34  to acquire the number of traffic signals and intersections present in the road. 
     The prescribed deceleration frequency determination zone is a zone set along the road on which the vehicle  3  is traveling. For example, setting using the point at which sudden braking occurred as the reference point, the deceleration frequency determination zone can be set as extending 1 kilometer ahead in the traveling direction of the vehicle  3 . Note that the distance of 1 kilometer is merely an example, and may be changed as appropriate. In addition, a position separated by a predetermined distance (e.g. 100 meters, changed as appropriate) ahead in the traveling direction of the vehicle  3  from the point where sudden braking occurred may be set as the reference point, and the deceleration frequency determination zone set as extending from the reference point to a position separated by a predetermined distance (e.g. 1 kilometer, changed as appropriate) ahead in the traveling direction of the vehicle  3 . The deceleration frequency determination zone may also be set so as to include the point where sudden braking occurred. As an example, the deceleration frequency determination zone may be set between two points, wherein one point is separated by a predetermined distance (e.g. 50 meters, changed as appropriate) opposite the traveling direction of the vehicle  3 , with the point where sudden braking occurred serving as the reference point, and the other point is separated by a predetermined distance (e.g. 1 kilometer, changed as appropriate) ahead in the traveling direction of the vehicle  3 , with the point where sudden braking occurred serving as the reference point. Thus, the deceleration frequency determination zone may be set such that the zone ahead of the point where sudden braking occurred is larger than the zone behind the point. As another example, the deceleration frequency determination zone may be set between two points, wherein one point is separated by a predetermined distance (e.g. 1 kilometer, changed as appropriate) opposite the traveling direction of the vehicle  3 , with the point where sudden braking occurred serving as the reference point, and the other point is separated by the same predetermined distance ahead in the traveling direction of the vehicle  3 , with the point where sudden braking occurred serving as the reference point. Thus, the deceleration frequency determination zone may be set such that the zone ahead of the point where sudden braking occurred and the zone behind the point are equidistant. 
     1-8. Percentage Calculation Unit 
     The percentage calculation unit  22  calculates the sudden braking percentage as a ratio of the sudden braking frequency, which is the number of times a braking operation was determined as a sudden braking operation by the sudden braking determination  19 , to the braking frequency that is counted by the brake counting unit  18 . The percentage calculation unit  22  also functions as a correction unit that corrects the sudden braking percentage to a higher value when sudden braking occurs and the vehicle deceleration frequency is determined as low for the road where sudden braking occurred. In the present embodiment, information pertaining to the braking frequency, the sudden braking frequency, and the sudden braking percentage is stored in the memory  32  in a form that can be referenced and updated by the percentage calculation unit  22 . 
     In the present embodiment, the percentage calculation unit  22  updates the sudden braking percentage to the latest percentage each time braking occurs. When braking occurs and the sudden braking determination unit  19  determines that the braking operation is a sudden braking operation, such information is input to the percentage calculation unit  22 . Note that to update the sudden braking frequency, the percentage calculation unit  22  makes a correction to be described later such that an increment for updating the sudden braking frequency becomes larger when the vehicle deceleration frequency is low for the road where sudden braking occurred. 
     Once information indicating that sudden braking occurred is input from the sudden braking determination unit  19 , the percentage calculation unit  22  also acquires information pertaining to the current position of the vehicle, i.e., the location of the point where sudden braking occurred, from the host vehicle position information acquisition unit  12 , and outputs such information to the vehicle deceleration frequency determination unit  14 . The percentage calculation unit  22  then acquires the determination result from the vehicle deceleration frequency determination unit  14 , and performs a correction based on the determination result using a correction coefficient as explained below. 
     The correction coefficient is a parameter stored in the memory  32 , and the value of the correction coefficient is set based on the correction rules  40  also stored in the memory  32 . The percentage calculation unit  22  sets the correction coefficient in accordance with the correction rules  40  and based on the determination result of the vehicle deceleration frequency determination unit  14 . Note that in the present embodiment, the correction rules  40  set the correction coefficient to 1.2 if the sudden braking occurred on a road with a low vehicle deceleration frequency, and set the correction coefficient to 1.0 if the sudden braking did not occur on a road with a low vehicle deceleration frequency. Further note that the above numerical values 1.2 and 1.0 are merely examples, and how the correction coefficient is set in each case may be changed as appropriate. 
     To update the sudden braking frequency, the percentage calculation unit  22  adds the product of 1 and the correction coefficient to the pre-update sudden braking frequency. However, no correction is made when the braking frequency is updated by the brake counting unit  18 . By updating the sudden braking frequency and the braking frequency as explained above, in the case where sudden braking occurs on a road with a low vehicle deceleration frequency, the increment for updating the sudden braking frequency is corrected so as to become larger. Consequently, the sudden braking percentage that is a ratio of the sudden braking frequency to the braking frequency can be corrected so as to increase. 
     The percentage calculation unit  22  calculates the sudden braking percentage, which is a ratio of the sudden braking frequency to the braking frequency, using Equation (1) below. 
       Sudden braking percentage (%)=(sudden braking frequency)/(braking frequency)×100  (1) 
     The sudden braking ratio calculated in this manner represents a ratio indicating that the driver&#39;s braking operation was not suitable. Conversely, if the sudden braking percentage is X %, then the percentage expressed as (100−X) % represents a ratio indicating that the braking operation was suitable. Thus, a smaller sudden braking percentage results in an evaluation of safer driving. 
     Note that the correction rules  40  referenced by the percentage calculation unit  22  can be updated using update information received from the central control server  2 . Such update processing is performed by the update processing unit  30 . Namely, if the update processing unit  30  receives update information regarding the correction rules  40  from the central control server  2  through the transmitter-receiver unit  11 , the update processing unit  30  updates the correction rules  40  stored in the memory  32  based on the update information. Accordingly, the rules may be changed as needed so as to set the sudden braking percentage to a more suitable value based on the total points thus far acquired (described later), the driver&#39;s skill level, driving history, and the like. 
     1-9. Evaluation Information Acquisition Unit 
     The evaluation information acquisition unit  23  acquires the evaluation information  61  based on the sudden braking percentage calculated by the percentage calculation unit  22 . As shown in  FIG. 1 , the evaluation information acquisition unit  23  here includes a point calculation unit  24 , a graph generation unit  25 , an advice acquisition unit  26 , and an external information acquisition unit  27 . As the evaluation information  61 , the evaluation information acquisition unit  23  acquires point information  62 , advice information, evaluation graph information  64 , the ranking information  65 , and the level information  66 . In addition, the point rules  38  and the advice data  37  referenced by the evaluation information acquisition unit  23  are stored in the memory  32 .  FIGS. 3 and 4  show an example of a screen displaying the evaluation information  61  acquired by the evaluation information acquisition unit  23  on the display input device  47 . Note that the advice information is not shown. Here,  FIG. 3  is an example of a total evaluation screen for displaying a result of a comprehensive evaluation regarding the sudden braking percentage thus far, and  FIG. 4  is an example of a guidance screen that display the evaluation graph information  64  for sequentially showing changes in the sudden braking percentage during travel of the vehicle  3 . Note that the example of  FIG. 4  shows the level information  66  and a guidance map for route guidance in addition to the evaluation graph information  64 . 
     The point calculation unit  24  calculates points to be assigned in accordance with the sudden braking percentage. At such time, the point calculation unit  24  refers to the point rules  38  stored in the memory  32 , and calculates the points to be assigned based on the point rules  38 . The point rules  38  are rules that specify the relationship between the sudden braking percentage calculated by the percentage calculation unit  22  and the assigned points. As an example, in the point rules  38  of the present embodiment, the sudden braking percentage is designated as X % and (100−X) % calculated. The point rules  38  also specify that 1 point is assigned for every 1%. However, if correcting the sudden braking frequency for calculating the sudden braking percentage causes the sudden braking percentage to exceed 100%, with the sudden braking percentage calculated by the percentage calculation unit  22  per trip between turning the main power source of the vehicle  3  on and off, then zero points are assigned (i.e., no points are assigned). Alternatively, after finding (X−100) %, 1 point may be subtracted for every 1%. 
     The point calculation unit  24  also integrates the points per trip calculated as described above and calculates the total points acquired thus far. The total points may be integrated and summed per prescribed period, e.g. every year, and then reset to zero once the year changes and integrated again. Alternatively, the total points may be an integrated value of the total points acquired thus far. The points per trip and total points calculated by the point calculation unit  24  are stored in the memory  32  as vehicle point data  39 . In addition, based on the vehicle point data  39  stored in the memory  32 , the point calculation unit  24  displays the point information  62 , which represents the total points and points that were acquired from previous travel (previously acquired points), on the display input device  47 . In the example shown in  FIG. 3 , such point information  62  is displayed in part of the total evaluation screen. 
     The point rules  38  referenced by the point calculation unit  24  can be updated using update information received from the central control server  2 . Such update processing is performed by the update processing unit  30 . Namely, if the update processing unit  30  receives update information regarding the point rules  38  from the central control server  2  through the transmitter-receiver unit  11 , the update processing unit  30  updates the point rules  38  stored in the memory  32  based on the update information. Accordingly, the rules may be changed as needed so that the assigned points become a more appropriate value, or changed so as to increase the assigned points for a limited time. Further note that the content of the point rules  38  above is merely one example, and any content may be set for the rules as appropriate. Therefore, the point rules  38  may be suitably set such that the assigned points vary depending on the distance traveled by the vehicle  3  per trip even though the sudden braking percentage is the same. 
     The graph generation unit  25  generates a graph display that visually represents a safe driving percentage at certain times. The safe driving percentage is derived from the sudden braking percentage and represents the ratio of safe driving in relation to braking. The safe driving percentage (%) is calculated as (100−X) %, where X % is the sudden braking percentage. However, if the sudden braking percentage exceeds 100% due to a correction, the safe driving percentage is set to 0%. Specifically, the graph generation unit  25  generates the evaluation graph information  64  for sequentially showing changes in the safe driving percentage during travel of the vehicle  3 , as illustrated in  FIG. 4 . The graph generation unit  25  also displays the generated evaluation graph information  64  on the display input device  47 . The evaluation graph information  64  includes a graph of the current value of the safe driving percentage and a graph of the past average value of the safe driving percentage. These graphs are arranged side by side so they can be compared against one another. Here, the graph of the current value of the safe driving percentage displays the safe driving percentage for a route traveled after turning on the main power source until the current time, and is sequentially updated as the vehicle  3  travels. The graph of the past average value of the safe driving percentage displays the average value of past information regarding the safe driving percentage for routes traveled between turning the main power source on and off, and the value is updated for each trip of the vehicle  3 . Both graphs are shown in the example as bar graphs. Note that information stored in the navigation device  1  or stored per vehicle  3  in the central control server  2  may be used as the information regarding past safe driving percentages. 
     The advice acquisition unit  26  acquires advice information with content that corresponds to the sudden braking percentage. Here, the advice acquisition unit  26  reads out and acquires advice information with content that corresponds to the sudden braking percentage from the advice data  37  stored in the memory  32 . The advice acquisition unit  26  also displays the acquired advice information on the display input device  47 . The advice information is statement information for communicating to the driver evaluation content that corresponds to the sudden braking percentage. For example, if the sudden braking percentage is low, a statement commending this fact is acquired as the advice information. Meanwhile, if the sudden braking percentage is high, a statement encouraging the driver to have a higher awareness of safe driving in relation to braking is acquired as the advice information. 
     The advice data  37  stored in the memory  32  can be updated using update information received from the central control server  2 . Such update processing is performed by the update processing unit  30 . Namely, if the update processing unit  30  receives update information regarding the advice data  37  from the central control server  2  through the transmitter-receiver unit  11 , the update processing unit  30  updates the advice data  37  stored in the memory  32  based on the update information. Accordingly, the content of the advice information may be changed as needed to more suitable content by changing the content of the advice information depending on the driving history or driving habits of the driver, for example. 
     The external information acquisition unit  27  executes a process to acquire the evaluation information  61  from the central control server  2 , which is provided outside the vehicle  3 . More specifically, the external information acquisition unit  27  communicates with the central control server  2  through the transmitter-receiver unit  11 , and receives the evaluation information  61  generated by comparing the ranking information  65  and level information  66  of other vehicles  3 . As described later, the central control server  2  is provided in communication with the navigation devices  1  installed in the plurality of vehicles  3 , and collects and sums information regarding the sudden braking percentage from the plurality of vehicles  3 . In the present embodiment, the central control server  2  collects from the navigation device  1  of each vehicle  3  and sums information regarding the points assigned depending on the sudden braking percentage, as well as information regarding the braking frequency and the post-correction sudden braking frequency, which serve as source information for calculating the sudden braking percentage. Using the sum result, the central control server  2  then generates the ranking information  65  and the level information  66 . The external information acquisition unit  27  of the navigation devices  1  request and acquire the ranking information  65  and the level information  66  generated in this manner from the central control server  2  at a predetermined timing. In the present embodiment, the external information acquisition unit  27  requests the ranking information  65  and the level information  66  from the central control server  2  when the main power source of the vehicle  3  mounted with the navigation device  1  is turned on. 
     The ranking information  65  indicates the ranking of the vehicles  3  as compared to other vehicles  3  in terms of the sudden braking percentage or the safe driving percentage that was calculated based on this. The ranking information  65  may be information regarding a ranking of average values for the sudden braking percentage of the vehicles within a predetermined period, or a ranking of the total points acquired by the vehicles within a predetermined period. Here, various periods may be set as the predetermined period, such as one year, one month, one week, or one day. The external information acquisition unit  27  also displays the acquired ranking information  65  on the display input device  47 . In the present embodiment, as shown in the example of  FIG. 3 , the ranking information  65  includes a ranking of the point totals acquired every month by each vehicle  3  compared to other vehicles  3 , and arrow images that indicate whether the ranking has increased or decreased compared to the previous month. 
     The level information  66  indicates the level assigned based on the past sudden braking percentage of each vehicle  3  as compared to other vehicles  3  or the safe driving percentage that was calculated based on this. The level information  66  may be information regarding the level to which each vehicle  3  belongs when the vehicles are divided into a plurality of levels depending on the ranking of average values for the sudden braking percentage of the vehicles within a predetermined period, the ranking of the total points acquired by the vehicles  3  within a predetermined period, or the total points acquired by the vehicles  3  thus far. In the present embodiment, the level information  66  is determined by raising or lowering the current level depending on the ranking of the total points acquired in a predetermined period (e.g. in one year). Here, the categories of A, B, C and so on, or the categories of 1, 2, 3 and so on may be used as levels. The external information acquisition unit  27  also displays the acquired level information  66  on the display input device  47 . In the present embodiment, as shown in the example of  FIG. 3 , the level information  66  uses the levels of A, B, C and so on, and the example in the figure indicates that the vehicle  3  resides at the B level. 
     1-10. Main Power Source Monitoring Unit 
     The main power source monitoring unit  28  monitors the state of a main power source switch  4  of the vehicle  3 . A state in which the main power source switch  4  is on and power is supplied to the components of the vehicle  3  is determined as an on state of the main power source. A state in which the main power source switch  4  is off and power is not supplied to the components of the vehicle  3  is determined as an off state of the main power source. 
     1-11. Send Processing Unit 
     The send processing unit  29  executes a process to send information regarding the sudden braking percentage to the central control server  2  at a predetermined timing. More specifically, when the main power source of the vehicle  3  installed with the navigation device  1  is turned off, the send processing unit  29  executes a process to send information regarding the sudden braking percentage between turning the main power source on and off to the central control server  2 . The on/off status of the main power source is determined by the main power source monitoring unit  28 . In the present embodiment, the send processing unit  29  sends to the central control server  2  information regarding the point information per trip assigned depending on the sudden braking percentage between turning the main power source on and off, as well as information regarding the braking frequency and the post-correction sudden braking frequency, which serve as source information for calculating the sudden braking percentage. 
     2. Configuration of Central Control Server 
     The configuration of the central control server  2  will now be described. As shown in  FIG. 2 , the central control server  2  is provided in communication with the plurality of navigation devices  1  that are respectively installed in the plurality of vehicles  3 . The central control server  2  collects and sums information regarding the sudden braking percentage from the navigation devices  1 , and generates the evaluation information  61  for the navigation devices  1  based on the summed information. The central control server  2  also distributes the generated evaluation information  61  in accordance with requests from the navigation devices  1 . 
     The components of the central control  2  shown in  FIG. 2  each have as its core member a computation processing device such as a CPU or the like that is one of mutually shared and independently utilized. Each component executes various processes on received data that may be implemented by hardware, software (a program), or via a combination of both hardware and software. In the present embodiment, the central control server  2  includes a transmitter-receiver unit  52 , a storage processing unit  53 , a sum processing unit  54 , and a distribution processing unit  55 . Each component is also configured to exchange information with the other components via wireless communication using a digital transfer bus or the like. If each component is implemented through software (a program), the software is stored in a storage unit such as a RAM or ROM to which the computation processing device can refer. A user database  51  also has a hardware configuration that includes a storage medium (a storage unit) that is capable of storing and re-writing information, such as a hard disk drive or a flash memory. The configuration of each component of the central control server  2  according to the present embodiment will be explained in detail below. 
     2-1. Transmitter-Receiver Unit 
     The transmitter-receiver unit  52  includes a communication device that sends data to the navigation device  1  installed in the plurality of vehicles  3  and receives data from the navigation device  1  by wireless communication via a wireless base station or the like. The wireless communication method is used in common by the transmitter-receiver unit  11  of the navigation device  1 . As explained above, in the present embodiment, the transmitter-receiver unit  52  receives from the navigation device  1  information regarding the sudden braking percentage, more specifically, information regarding the points assigned depending on the sudden braking percentage, as well as information regarding the braking frequency and the post-correction sudden braking frequency, which serve as source information for calculating the sudden braking percentage. In addition, the transmitter-receiver unit  52  sends the evaluation information  61  that is based on a comparison with other vehicles  3 , such as the ranking information  65  and the level information  66 , to the navigation device  1 . The transmitter-receiver unit  52  also sends the update information for updating the advice data  37 , the point rules  38 , and the correction rules  40  stored in the memory  32  of the navigation device  1 . 
     2-2. Storage Processing Unit 
     The storage processing unit  53  executes a process to store information regarding the sudden braking percentage, which was received by the transmitter-receiver unit  52  from the navigation device  1  installed in each vehicle  3 , in the user database  51  as sorted per vehicle  3 . As explained above, in the present embodiment, the information regarding the sudden braking percentage includes information regarding the points assigned depending on the sudden braking percentage, as well as information regarding the braking frequency and the post-correction sudden braking frequency, which serve as source information for calculating the sudden braking percentage. Here, the information regarding the points assigned depending on the sudden braking percentage is specifically point information per trip that is assigned depending on the sudden braking percentage between turning the main power source on and off. Also, the information regarding the braking frequency and the post-correction sudden braking frequency is also information per trip between turning the main power source on and off. Such information is sent from the navigation device  1  as information per trip of the vehicle  3  when the main power source of the vehicle  3  is turned off, and received by the transmitter-receiver unit  52 . The storage processing unit  53  stores information regarding the received sudden braking percentage in the user database  51  as associated with identification information for each vehicle  3  and information regarding the date and time received. Here, the identification information of the vehicles  3  may use the license plate numbers of the vehicles  3 , or use identification codes of the navigation devices  1  or vehicles  3 , for example. 
     2-3. Sum Processing Unit 
     The sum processing unit  54  executes a process to sum information regarding the sudden braking percentage for each vehicle  3  stored in the user database  51  and generate the evaluation information  61  for each vehicle  3  (each navigation device  1 ). Specifically, the sum processing unit  54  sums the point information per trip received from each vehicle  3  for each predetermined period and generates the ranking information  65  that represents the ranking of point totals comparing the plurality of vehicles  3 . In the present embodiment, the sum processing unit  54  computes the total points acquired per month by each vehicle  3 , and generates the ranking information  65  that represents the ranking as compared to other vehicles  3 . Furthermore, the sum processing unit  54  sums the points acquired within a predetermined period by each vehicle  3 , and generates the level information  66  that represents the level assigned in accordance with the sum result. In the present embodiment, the sum processing unit  54  determines the level of each vehicle  3  by raising the level for a higher rank or reducing the level for a lower rank depending on the ranking of the total points acquired in the predetermined period (e.g. in one year). Note that the level until the initial passage of the predetermined period may be set to any level, such as the lowest level or an intermediate level. The generated ranking information  65  and level information  66  are stored in the user database  51  as associated with the identification information of each vehicle  3 . 
     The sum processing unit  54  also integrates information regarding the points per trip received from the vehicles  3  and calculates the total points acquired thus far. As explained above, the total points are an integrated value that is integrated per predetermined period, or an integrated value of all the points acquired thus far. Information regarding the calculated total points is stored in the user database  51  as associated with the identification information of each vehicle  3 . Information regarding the total points thus stored in the user database  51  is used for backing up and confirming information regarding the total points stored in the memory  32  of each navigation device  1 . Therefore, such information matches information regarding the total points stored in the memory  32  of the navigation device  1  as the vehicle point data  39 . 
     2-4. Distribution Processing Unit 
     The distribution processing unit  55  executes a process to read out from the user database  51  the ranking information  65  and the level information  66 , which serve as the evaluation information  61  generated by the sum processing unit  54 , in response to a request from the external information acquisition unit  27  of each navigation device  1 , and then sends such information to each navigation device  1 . When update information is generated for updating the point rules  38  or the advice data  37  by an update information generation unit (not shown), the distribution processing unit  55  also executes a process to send such update information to the navigation device  1 . 
     3. Procedure for Operation Processing 
     Next, a procedure for a safe driving evaluation process (a safe driving evaluation method) that is executed in the navigation device  1  according to the present embodiment will be explained.  FIG. 5  is a flowchart that shows an overall procedure for the safe driving evaluation process according to the present embodiment.  FIG. 6  is a flowchart that shows a procedure for a sudden braking percentage calculation process at # 05  of  FIG. 5 . The description below will follow the flowcharts. 
     3-1. Overall Procedure for Safe Driving Evaluation Processing 
     The overall procedure for the safe driving evaluation processing will now be described. As shown in  FIG. 5 , if the main power switch  4  of the vehicle  3  installed with the navigation device  1  is turned on (YES at # 01 ), the external information acquisition unit  27  requests the ranking information  65  and the level information  66 , which serve as the evaluation information  61  for the vehicle  3 , from the central control server  2 , and receives the information (# 02 ). The total evaluation screen is then displayed (# 03 ). As shown in  FIG. 3 , the total evaluation screen includes a display of the point information  62  that indicates the points acquired during previous travel (previously acquired points) and the total points, as well as a display of the ranking information  65  and the level information  66 . Note that, although not shown in the figure, the advice information is also displayed together with the above information. Here, the point information  62  is calculated by the point calculation unit  24  and acquired from the vehicle point data  39  stored in the memory  32 . The advice information is acquired by the advice acquisition unit  26  reading out advice information with content that corresponds to the sudden braking percentage during previous travel from the advice data  37  stored in the memory  32 . The ranking information  65  and the level information  66  are received and acquired from the central control server  2  at # 02 . The total evaluation screen is formed by arranging the above information in accordance with a predetermined format. 
     If the vehicle  3  has started traveling (YES at # 04 ), the percentage calculation unit  22  executes a process to calculate the sudden braking percentage (# 05 ). The sudden braking percentage calculation processing will be described in detail later based on the flowchart in  FIG. 6 . Next, the graph generation unit  25  generates and displays the evaluation graph information  64  (# 06 ). As shown in  FIG. 4 , the evaluation graph information  64  is a graph display that visually represents the safe driving percentage derived from the sudden braking percentage at certain times. The evaluation graph information  64  includes a graph of the current value of the safe driving percentage and a graph of the past average value of the safe driving percentage. The processing at # 05  and # 06  is repeatedly executed until the main power source is turned off. Accordingly, once the main power source of the vehicle  3  is turned on, until the main power source is turned off (NO at # 07 ), the sudden braking percentage at certain times is calculated as needed and the evaluation graph information  64  that shows the safe driving percentage at certain times is displayed on the display input device  47 . 
     If the main power source is subsequently turned off (YES at # 07 ), the send processing unit  29  sends information regarding the sudden braking percentage between turning the main power source on and off to the central control server  2  (# 08 ). Here, as explained above, the information regarding the sent sudden braking percentage includes the point information per trip, as well as information regarding the braking frequency and the post-correction sudden braking frequency, which serve as source information for calculating the sudden braking percentage. The point information per trip in such case is information regarding the points assigned depending on the sudden braking percentage between turning the main power source on and off. Note that the sudden braking percentage between turning the main power source on and off is equivalent to the sudden braking percentage at certain times as calculated at # 05  before the main power source is turned off. The overall procedure of the safe driving evaluation processing is then ended. 
     3-2. Procedure for Sudden Braking Percentage Calculation Processing 
     The procedure for the sudden braking percentage calculation processing at # 05  in  FIG. 5  will be described next. As shown in  FIG. 6 , if the brake signal detection unit  15  detects the brake signal (YES at # 11 ), the brake counting unit  18  adds 1 to the braking frequency to update the braking frequency (# 12 ). The process next proceeds to determine whether the brake assist signal detection unit  17  has detected the brake assist signal (# 13 ). If the brake assist signal has been detected (YES at # 13 ), the vehicle deceleration frequency determination unit  14  determines whether the vehicle deceleration frequency is low for the road where sudden braking occurred (# 14 ). If it is determined that the vehicle deceleration frequency is low (YES at # 14 ), the percentage calculation unit  22  sets the correction coefficient to 1.2. However, if it is determined that the vehicle deceleration frequency is not low (NO at # 14 ), the percentage calculation unit  22  sets the correction coefficient to 1.0. The percentage calculation unit  22  then adds the product of 1 and the correction coefficient to the pre-update sudden braking frequency (# 17 ). The process subsequently stands by until the brake signal turns off (NO at # 18 ). When the brake signal turns off (YES at # 18 ), the percentage calculation unit  22  updates the sudden braking percentage (# 20 ), after which the process returns to # 11 . 
     Meanwhile, if the brake assist signal is not detected at # 13  (NO at # 13 ), the process proceeds to determine whether the brake signal is off (# 19 ). If the brake signal is not off (NO at # 19 ), the process returns to # 13 . However, if the brake signal is off (YES at # 19 ), the percentage calculation unit  22  updates the sudden braking percentage (# 20 ), after which the process returns to # 11 . 
     After returning to # 11 , the process stands by until the brake signal is detected by the brake signal detection unit  15  again (NO at # 11 ). Once the brake signal is detected (YES at # 11 ), the above processing is executed again. In other words, the above processing is repeatedly executed each time the vehicle  3  brakes. 
     Other Embodiments 
     (1) In the embodiment described above, as an example, a case was explained in which the increment for updating the sudden braking frequency, which is the numerator of Equation (1) for calculating the sudden braking percentage, is corrected so as to be larger than normal if sudden braking occurs on a road with a low vehicle deceleration frequency. However, the embodiments of the present invention are not limited to this example. Namely, in another preferred embodiment of the present invention, the braking frequency, i.e., the denominator of Equation (1), may be corrected. For example, the sudden braking frequency is updated by adding 1 to the pre-update sudden braking frequency, and the braking frequency is updated by adding a product of 1 and the correction coefficient to the pre-update braking frequency. In such case, unlike the above embodiment, the correction rules  40  preferably set the correction coefficient to a value under 1.0 if the sudden braking occurred on a road with a low vehicle deceleration frequency, and set the correction coefficient to 1.0 if the sudden braking did not occur on a road with a low vehicle deceleration frequency. Therefore, the sudden braking percentage can be corrected to a higher value by correcting the increment for updating the braking encounter frequency to a smaller value. A configuration that corrects the increments of both the sudden braking frequency and the braking frequency may also be used, as well as a configuration that sets the increments when updating to 1 for both the sudden braking frequency and the braking frequency, without correcting either the sudden braking frequency or the braking frequency. Furthermore, a configuration may be used that sets the increments when updating to 1 for both the sudden braking frequency and the braking frequency, and corrects the sudden braking percentage by adding or subtracting a predetermined value to or from the sudden braking percentage calculated based on Equation (1) or by multiplying the sudden braking percentage by a predetermined coefficient. 
     In the embodiment described above, as an example, a case was explained in which the vehicle deceleration frequency determination unit  14  determines whether the vehicle deceleration frequency is low for the road where sudden braking occurred. However, the embodiments of the present invention are not limited to this example. Namely, in another preferred embodiment of the present invention, there may be many thresholds for determining the vehicle deceleration frequency for the road where sudden braking occurred, and the vehicle deceleration frequency determination unit  14  may determine the vehicle deceleration frequency for the road according to a plurality of levels. For example, the vehicle deceleration frequency determination unit  14  may determine the vehicle deceleration frequency for the road where sudden braking occurred as one of three levels, low, medium and high, and different correction coefficients may be set for each level. 
     (2) In the embodiment described above, as an example, a case was explained in which the sudden braking determination unit  19  determines whether sudden braking occurred based on whether the brake assist signal has been detected by the brake assist signal detection unit  17 . However, the embodiments of the present invention are not limited to this example. Namely, in another preferred embodiment of the present invention, the navigation device  1  may include an acceleration information detection unit that acquires information indicating an acceleration of the vehicle  3 . The determination regarding whether sudden braking occurred may then be based on the magnitude of deceleration acquired by the acceleration information detection unit. If the distance sensor  43  is provided with a sensor for detecting acceleration in such case, the acceleration information detection unit may acquire information indicating the acceleration of the vehicle  3  from the distance sensor  43 . In yet another preferred embodiment of the present invention, the navigation device  1  may include a speed information detection unit that acquires information indicating a speed of the vehicle  3 . The speed of the vehicle  3  before braking and the speed of the vehicle  3  after braking may then be detected, and the deceleration calculated based on a difference thereof. 
     (3) In the embodiment described above, as an example, a case was explained in which the vehicle deceleration frequency determination unit  14  determines whether the vehicle deceleration frequency is low for a road where sudden braking occurred based on the number of traffic signals and intersections present within a prescribed deceleration frequency determination zone, which is set using the point where sudden braking occurred as a reference point. However, the embodiments of the present invention are not limited to this example. Namely, in another preferred embodiment of the present invention, the map date 34 may be referenced to acquire the road type information for the road where sudden braking occurred, and the vehicle deceleration frequency determination unit  14  may determine whether the vehicle deceleration frequency for the road is low based on the road type information. For example, a road indicated as an expressway in the road type information may be determined as having a low vehicle deceleration frequency. 
     (4) In the embodiment described above, as an example, a case was explained in which the vehicle deceleration frequency determination unit  14  acquires the number of traffic signals and intersections present on the road based on the map data  34  stored in the map database  31  provided in the navigation device  1 . However, the embodiments of the present invention are not limited to this example. Namely, the information pertaining to the number of traffic signals and intersections may be acquired based on information provided by a facility outside the vehicle  3 , such as road traffic information or the like distributed from VICS (trademark: Vehicle Information and Communication System). 
     (5) In the embodiment described above, as an example, a case was explained in which the evaluation information acquisition unit  23  acquires the point information  62 , advice information, the evaluation graph information  64 , the ranking information  65 , and the level information  66  as the evaluation information  61 , and outputs them in a manner understandable to the driver. However, the embodiments of the present invention are not limited to this example. Namely, in another preferred embodiment of the present invention, only a portion of the above information may be acquired as the evaluation information  61 . In addition, various other information representing an evaluation pertaining to the sudden braking percentage may be acquired as the evaluation information  61 . 
     (6) In the embodiment described above, as an example, a case was explained in which the point calculation unit  24  provided in the navigation device  1  calculates the point for each trip and the total points acquired thus far, and stores these in the memory  32  of the navigation device  1 . However, the embodiments of the present invention are not limited to this example. Namely, information regarding the points per trip as calculated by the point calculation unit  24  may be sent to the central control server  2  and the total points for each vehicle  3  calculated in the central control server  2 . Alternatively, information regarding the sudden braking percentage per trip may be sent to the central control server  2 , and the points per trip as well as the total points calculated in the central control server  2 . In such case, the external information acquisition unit  27  acquires the information regarding the total points and the points per trip for the vehicle  3  from the central control server  2  through the transmitter-receiver unit  11  at a predetermined timing. 
     (7) The allocation of components respectively provided in the navigation device  1  and the central control server  2  as described in the above embodiment is but one example. Accordingly, aside from components that must be provided on the navigation device  1  side, such as the host vehicle position information acquisition unit  12 , each component may be provided in either the navigation device  1  or the central control server  2 . Therefore, in another preferred embodiment of the present invention, the overall configuration of the safe driving evaluation system may be provided in the navigation device  1  acting as the on-vehicle terminal device. Therefore, in yet another preferred embodiment of the present invention, the main configuration of the safe driving evaluation system may be entirely provided in the central control server  2  acting as the central control device. Here, the main configuration of the safe driving evaluation system includes the vehicle deceleration frequency determination unit  14 , the percentage calculation unit  22  acting as the correction unit and the percentage calculation unit, and the evaluation information acquisition unit  23 . 
     (8) In the embodiment described above, as an example, a case was explained in which the on-vehicle terminal device that structures the safe driving evaluation system according to the present invention is the navigation device  1 . However, the embodiments of the present invention are not limited to this example. Namely, in another preferred embodiment of the present invention, the on-vehicle terminal device that structures the safe driving evaluation system according to the present invention may be a control device of the vehicle  3  that is unrelated to the navigation device  1 . 
     The present invention is well suited for application to a safe driving evaluation system and a safe driving evaluation program that perform a safe driving evaluation based on a sudden braking percentage, which considers the necessity of braking at a location where sudden braking occurred.