Patent Publication Number: US-7904235-B2

Title: Driving evaluation apparatus, driving evaluation program, and driving evaluation method

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This is a continuation of application Ser. No. 11/154,674, filed Jun. 17, 2005, now U.S. Pat. No. 7,346,449 which is incorporated herein by reference. 
    
    
     This application claims the benefit of priority under 35USC §119 to Japanese Patent Application No. 2004-186389 filed on Jun. 24, 2004, the entire contents of which are incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a driving evaluation apparatus, a driving evaluation program and a driving evaluation method for evaluating a result of driving of a vehicle (fuel consumption, vehicle speed etc.) in certain driving interval on the basis of driving data of the driving interval. More particularly, the invention relates to a driving evaluation apparatus, a driving evaluation program and a driving evaluation method capable of properly evaluating a driving result while considering situations of various driving roads that cannot be improved by driving skills. 
     2. Related Art 
     Because of increasing environment awareness and for the purpose of reducing fuel cost in transportation business, an information system for assisting a driver to learn a driving skill to efficiently drive is in demand. In such a system, a driving evaluation method of evaluating driving from the viewpoint of fuel consumption rate (specific fuel consumption) on the basis of driving data is necessary. 
     For example, it is also possible to determine an evaluation value, by calculating fuel consumption rate of one day by dividing travel distance in driving data of one day by total fuel consumption amount and checking the fuel consumption rate with a fuel consumption statistic distribution or the like. In such a method, however, there is a problem such that the driver forgets a problem in his/her driving, so that effective assistance cannot be given. It is therefore important to evaluate a driving result in a time interval from a past relative short time to the present time point by using only interval driving data as driving data in the interval and immediately provide the evaluation result to the driver. 
     The situations (driving environments) of a driving road such as continuation of steep slopes and curves, traffic jam, and the like which exert an influence on the fuel consumption rate but cannot be controlled by driving skills vary according to intervals. Consequently, in evaluation of the driving result in the relatively short time interval, a case may occur such that although driving is efficient, due to relatively bad driving environments, the value of fuel consumption rate is low. On the contrary, a case may occur such that although, driving is inefficient, the driving environments are relatively good, so that the value of fuel consumption rate is high. To properly evaluate the result of driving in a relatively short time interval, it is important to calculate a variable related to the driving environments from interval driving data and make an evaluation in which the driving environments are properly reflected. 
     Japanese Patent No. 3,314,870 discloses a driving evaluation method capable of making an evaluation of interval driving data in which driving environments are reflected. According to the method, a value obtained by correcting a drive fuel consumption rate by an addition value in which driving environments are reflected is used as an evaluation value of the driving result. However, it is difficult to generate a proper point table for calculating the addition value. In the method, how the driving environments from the interval driving data is estimated is not clarified. Therefore, by this method, actually, it is difficult to make an evaluation of the interval driving data in which the driving environments are reflected. 
     As another driving evaluation method capable of making an evaluation of interval driving data in which the driving environments are reflected, there is a driving evaluation method in a vehicle-driving-state-evaluating-system disclosed in Japanese Patent Laid-Open No. 2002-362185. In the method, various “driving manners that deteriorate fuel consumption rate” defined on the basis of a domain knowledge of bad driving manners which deteriorate fuel consumption rate are detected from the interval driving data. The difference between actual fuel consumption amount of detected driving and a theoretical fuel consumption amount in the case of ideal driving without driving which deteriorates fuel consumption is calculated, and efficiency of driving is evaluated by the difference. Examples of “driving manners which deteriorate fuel consumption rate” are (1) excessive driving force, (2) over speed, (3) erroneous shifting, (4) racing, and (5) idling. For example, in determination of whether (1) excessive driving force is used or not, by calculating hill climbing resistance at the time of calculating driving force, a driving evaluation in which the driving environment of a hill in a driving road is reflected can be made. The method of detecting “driving manners which deteriorate fuel consumption rate” and evaluating the driving result has an advantage such that inefficient driving can be notified to the driver immediately after detection. 
     The method, however, has a problem such that since the driving result is evaluated on the basis of detection of pre-defined “driving manners which deteriorate fuel consumption rate”, even if inefficient driving which cannot be detected exists, it is ignored. Moreover, since it is difficult to define a driving manner that deteriorates fuel consumption rate in all of driving environments, even if driving is efficient, it may be evaluated inefficient depending on the driving environments. 
     SUMMARY OF THE INVENTION 
     According to an aspect of the present invention, there is provided a driving evaluation apparatus for evaluating a result of driving a vehicle in certain driving interval on the basis of driving data acquired at time of driving in the driving interval, comprising: an energy consumption efficiency calculator calculating an energy consumption efficiency in the driving interval, by using the driving data; a driving environment variable calculator calculating a driving environment variable indicative of an environment factor which exerts an influence on energy consumption by driving in the driving interval, on the basis of the driving data; a function storing unit storing a plurality of probability density functions or cumulative distribution functions having the energy consumption efficiency as a probability variable; a function selector selecting the probability density function or the cumulative distribution function corresponding to the calculated driving environment variable; and an evaluation value calculator calculating an evaluation value for evaluating a result of driving in the driving interval by using the selected probability density function or the selected cumulative distribution function and the calculated energy consumption efficiency. 
     According to an aspect of the present invention, there is provided a driving evaluation program for evaluating a result of driving a vehicle in certain driving interval on the basis of driving data acquired at time of driving in the driving interval and for making a computer execute, comprising: calculating an energy consumption efficiency in the driving interval, by using the driving data; calculating a driving environment variable indicative of an environment factor which exerts an influence on energy consumption by driving in the driving interval, on the basis of the driving data; selecting a probability density function or a cumulative distribution function corresponding to the calculated driving environment variable from a plurality of probability density functions or cumulative distribution functions having the energy consumption efficiency as a probability variable; and calculating an evaluation value for evaluating a result of driving in the driving interval by using the selected probability density function or the selected cumulative distribution function and the calculated energy consumption efficiency. 
     According to an aspect of the present invention, there is provided a driving evaluation method for evaluating a result of driving a vehicle in certain driving interval on the basis of driving data acquired at time of driving in the driving interval, comprising: calculating an energy consumption efficiency in the driving interval, by using the driving data; calculating a driving environment variable indicative of an environment factor which exerts an influence on energy consumption by driving in the driving interval, on the basis of the driving data; selecting a probability density function or a cumulative distribution function corresponding to the calculated driving environment variable from a plurality of probability density functions or cumulative distribution functions having the energy consumption efficiency as a probability variable; and calculating an evaluation value for evaluating a result of driving in the driving interval by using the selected probability density function or the selected cumulative distribution function and the calculated energy consumption efficiency. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a configuration diagram of a driving evaluation apparatus according to an embodiment of the invention; 
         FIG. 2  is a configuration diagram of interval fuel information calculator in  FIG. 1 ; 
         FIG. 3  is a diagram showing an example data of interval fuel consumption amount; 
         FIG. 4  is a diagram showing an example of interval fuel information; 
         FIG. 5  is a configuration diagram showing part of driving environment variable calculator in  FIG. 1 ; 
         FIG. 6  is a configuration diagram showing part of the driving environment variable calculator in  FIG. 1 ; 
         FIG. 7  is a configuration diagram showing part of the driving environment variable calculator in  FIG. 1 ; 
         FIG. 8  is a diagram showing an example calculation of a driving environment variable; 
         FIG. 9  is a diagram showing an example of a distribution function; 
         FIG. 10  is a configuration diagram of the fuel consumption rate evaluator of  FIG. 1 ; 
         FIG. 11  is a diagram showing an example calculation of reference fuel consumption rate; 
         FIG. 12  is a diagram showing an example of an interval fuel consumption evaluation value; and 
         FIG. 13  is a diagram showing an example of updating of a distribution function. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     An embodiment of the invention will be described hereinbelow with reference to the drawings. 
       FIG. 1  is a configuration diagram showing an embodiment of a driving evaluation apparatus of the invention. As shown in  FIG. 1 , the driving evaluation apparatus comprises interval driving data storing unit  101 , interval fuel information calculator  102 , interval fuel information storing unit  103 , driving environment variable calculator  104 , driving environment variable storing unit  105 , distribution function selector  106 , function set storing unit  107 , distribution function storing unit  108 , fuel consumption rate evaluator  109 , evaluation value storing unit  110 , and distribution function updater  111 . 
     In the interval driving data storing unit  101 , driving data of a vehicle, which is a collection of sampling data sampled at predetermined period (for example, 200 msec) in certain driving interval, is stored. The driving interval has certain time range (for example, 1 minute or 10 seconds etc.) from start point time to end point time. The vehicle includes, for example, truck, internal combustion engine vehicle, electric vehicle, electric bicycle, and bike. In the following description, an internal combustion engine vehicle is assumed. The kinds of driving data of a vehicle vary according to sensors mounted on the vehicle. In present example, information of at least fuel consumption amount (energy consumption amount), vehicle speed, engine rotational speed, and clutch state is necessary. Preferably, information such as vehicle position, vehicle altitude, accelerator operation amount, vehicle acceleration, vehicle weight, and the like is included in time sequence. In the case where the vehicle is an electric vehicle or electric bicycle, the energy consumption amount corresponds to, for example, electricity consumption amount. 
     The interval fuel information calculator  102  calculates information with respect to fuel consumption in the driving interval by using the interval driving data stored in the interval driving data storing unit  101  and stores the calculated information as interval fuel information into the interval fuel information storing unit  103 . The interval fuel information, for example, may include fuel consumption rate (energy consumption rate). The fuel consumption rate is, for example, obtained as follows. 
     Travel distance D in the driving interval is calculated by adding the vehicle speed data. By calculating the sum of the fuel consumption amount, total fuel consumption amount F is obtained. By D/F, the interval fuel consumption rate is computed. The interval fuel consumption rate, for example, corresponds energy consumption efficiency. 
     Alternately, the interval fuel consumption rate may be computed as follows. 
     Fuel consumption amount obtained by subtracting a fuel amount consumed by racing or excessive idling regarded as inefficient driving irrespective of driving environments from the total fuel consumption amount F is computed. The travel distance D is divided by the fuel consumption amount, thereby obtaining interval fuel consumption rate M. 
     In the following description, the interval fuel consumption rate M is assumed. As will be described later, by using the interval fuel consumption rate M as one of interval fuel information, the skill of driving can be purely evaluated. The interval fuel information calculator  102  will be described in more detail hereinbelow. 
       FIG. 2  is a configuration diagram of the interval fuel information calculator  102  in  FIG. 1 . As shown in  FIG. 2 , the interval fuel information calculator  102  has racing fuel consumption amount calculator  201 , racing fuel consumption amount storing unit  202 , idling fuel consumption rate calculator  203 , idling fuel consumption amount storing unit  204 , and interval fuel consumption rate calculator  205 . 
     The racing fuel consumption amount calculator  201  detects a domain in which racing is performed by using the interval driving data and calculates racing fuel consumption amount Fk as fuel amount consumed in the domain. The calculated fuel consumption amount Fk is stored in the racing fuel consumption amount storing unit  202 . The racing can be detected by extracting a time domain in which the speed is close to zero, the clutch is disengaged, and the engine rotational speed is high. 
     The idling fuel consumption amount calculator  203  detects a time domain in which idling is performed by using the interval driving data. In the case where idling is performed for time threshold the or longer in the domain, it is regarded as unnecessary idling. When unnecessary idling is detected, idling fuel consumption amount Fa as fuel amount consumed in the domain is calculated and stored in the idling fuel consumption amount storing unit  204 . The idling can be detected by extracting a time domain in which speed is close to zero and engine rotational speed is close to predetermined idle speed. 
     The interval fuel consumption rate calculator  205  calculates the sum of speeds, thereby obtaining the travel distance. D in the driving interval and computes the above total fuel consumption amount F. The interval fuel consumption rate calculator  205  calculates interval fuel consumption rate M as follows.
 
 M=D /( F−Fa−Fk )
 
The interval fuel consumption rate calculator  205  stores M, Fa, Fk, and F as the interval fuel information into the interval fuel information storing unit  103 . In the embodiment, although the value obtained by dividing fuel consumption amount by distance is used as fuel consumption rate, a value obtained by dividing distance by fuel consumption amount may be used.
 
       FIG. 3  is a diagram for explaining fuel consumption amount in the driving interval from time t1 to time t2. Domains  301 ( 1 ) and  301 ( 2 ) in the diagram show fuel amounts consumed by normal driving. A domain  302  indicates a fuel amount consumed by allowable idling within time the from the idling start. A domain  303  indicates a fuel amount (Fa) consumed by unnecessary idling over the time the from the start of idling. A domain  304  indicates a fuel amount (Fk) consumed by racing. In the example, by dividing the fuel consumption amount corresponding to sum area of the domains  301 ( 1 ),  301 ( 2 ), and  302  by the driving distance D in the driving interval, the interval fuel consumption rate M is calculated. 
       FIG. 4  shows an example of the interval fuel information (M, Fa, Fk, and F) and shows the interval fuel consumption rate M, idling fuel consumption amount Fa, racing fuel consumption amount Fk, and total fuel consumption amount F. As described above, the interval fuel information (M, Fa, Fk, and F) is stored in the interval fuel information storing unit  103 . 
     Referring again to  FIG. 1 , the driving environment variable calculator  104  calculates the value of a driving environment variable indicative of the situations of a drive path which exerts an influence on fuel consumption but cannot be changed by a driving skill, using the interval driving data stored in the interval driving data storing unit  101 . The value of the driving environment variable calculated is stored in the driving environment variable storing unit  105 . There may be plural kinds of driving environment variables. 
       FIG. 5  is a configuration diagram of a part for calculating a driving road resistance as one of driving environment variables in the driving environment variable calculator  104 . The driving road resistance is, as will be described in detail hereinbelow, resistance to a vehicle, which is almost continue to be brought to the vehicle during a driving, irrespective of driving skill. As shown in  FIG. 5 , the driving environment variable calculator  104  has driving force calculator  501 , air resistance calculator  502 , accelerating resistance calculator  503 , driving variable storing unit  504 , and driving road resistance calculator  505 . 
     The driving force calculator  501  calculates driving force F(t) in the vehicle travel direction at each of time points (sampling points) “t” in the driving interval, and stores the calculated driving force F(t) into the driving variable storing unit  504 . The driving force can be obtained by preparing, for example, a torque map for calculating a torque τe(t) supposed to be output from an engine on the basis of the fuel consumption amount and the engine rotational speed at each time point, and calculated by the following equation.
 
 F ( t )=α* G ( t )*τ e ( t )/ r  
 
where G(t) denotes speed reducing ratio of a gear at time (t), α denotes transfer efficiency of the gear, and r indicates radius of a tire. They are given in advance in accordance with the car model.
 
     The air resistance calculator  502  calculates air resistance RI(t) in the vehicle travel direction at each time point “t” in the driving interval by using the interval driving data and stores the calculated air resistance RI(t) into the driving variable storing unit  504 . The air resistance can be calculated by, for example, the following equation using speed v(t) at each time point.
 
 RI ( t )=β* v ( t ) 2  
 
where β denotes coefficient of air resistance and is preliminarily given in accordance with the car model.
 
     The accelerating resistance calculator  503  calculates accelerating resistance (resistance generated at the time of acceleration/deceleration) Ra(t) in the vehicle travel direction at each time point “t” in the driving interval, and stores the calculated accelerating resistance Ra(t) into the driving variable storing unit  504 . The accelerating resistance can be obtained by, for example, calculating vehicle weight m(t) and acceleration a(t) in the vehicle travel direction at each time point and by using the following.
 
 Ra ( t )= m ( t )* a ( t )
 
     The driving road resistance calculator  505  calculates driving road resistance by the following using driving force F(t), air resistance RI(t), and accelerating resistance Ra(t) stored in the driving variable storing unit  504 .
 
Average(F(t)−RI(t)−Ra(t))
 
     The calculated driving road resistance is stored as one of the driving environment variables into the driving environment variable storing unit  105 . 
     Average ( ) denotes the function for calculating an average value of arguments. Resistance obtained by subtracting the air resistance and the accelerating resistance from the driving force is regarded as resistance such as hill climbing resistance (resistance by inclination of a hill) or rolling resistance (resistance generated when a tire rolls on the road surface), which cannot be controlled by a driving skill. Therefore, the driving road resistance can be considered as a feature quantity in which the situations of a driving are properly reflected from the viewpoint of resistance. 
       FIG. 6  is a configuration diagram of a part for calculating a kinetic energy change as one of the driving environment variables in the driving environment variable calculator  104 . As shown in  FIG. 6 , the driving environment variable calculator  104  has vehicle weight calculator  601 , vehicle speed calculator  602 , driving variable storing unit  504 , and kinetic energy change calculator  603 . 
     The vehicle weight calculator  601  calculates vehicle weights m(t1) and m(t2) at start point time t1 and end point time t2 in the driving interval by using, for example, the value m(t) of a vehicle weight sensor in the interval driving data. The calculated vehicle weights m(t1) and m(t2) are stored in the driving variable storing unit  504 . 
     The vehicle speed calculator  602  calculates vehicle speeds v(t1) and v(t2) at the start point time t1 and the end point time t2 in the driving interval by using, for example, the value v(t) of the vehicle speed sensor. The calculated vehicle speeds v(t1) and v(t2) are stored in the driving variable storing unit  504 . 
     The kinetic energy change calculator  603  calculates the kinetic energy change amount by the following equation using the vehicle weights m(t1) and m(t2) and vehicle speeds v(t1) and v(t2) stored in the driving variable storing unit  504 .
 
(m(t2)*v(t2) 2 −m(t1)*v(t1) 2 )/2
 
     The calculated kinetic energy change amount is stored as one of the driving environment variables into the driving environment variable storing unit  105 . 
     It is assumed that the driver can change the vehicle speed in the driving interval by his/her intention but cannot select the speeds at the interval start and end points. In this case, the kinetic energy change amount can be regarded as a feature quantity in which the situations of the drive path as necessity of acceleration/deceleration are reflected. 
       FIG. 7  is a configuration diagram of a part for calculating the potential energy change as one of the driving environment variables in the driving environment variable calculator  104 . As shown in  FIG. 7 , the driving environment variable calculator  104  has the vehicle weight calculator  601 , vehicle altitude (height) calculator  702 , driving variable storing unit  504 , and potential energy change calculator  703 . 
     The vehicle weight calculator  601  calculates the vehicle weights m(t1) and m(t2) at the start point time t1 and end point time t2 in the driving interval by using, for example, the value m(t) of a vehicle weight sensor in the interval driving data. The calculated vehicle weights m(t1) and m(t2) are stored in the driving variable storing unit  504 . 
     The vehicle altitude calculator  702  calculates vehicle altitudes h(t1) and h(t2) at the start point time t1 and the end point time t2 in the driving interval by using, for example, altitude information h(t) of a GPS. The calculated vehicle altitudes h(t1) and h(t2) are stored in the driving variable storing unit  504 . 
     The potential energy change calculator  703  calculates the potential energy change amount by the following equation using the vehicle weights m(t1) and m(t2) and vehicle altitudes h(t1) and h(t2) stored in the driving variable storing unit  504 .
 
g*(m(t2)*h(t2)−m(t1)*h(t1))
 
The calculated potential energy change amount is stored as one of the driving environment variables into the driving environment variable storing unit  105 .
 
     It is assumed that the driver can change the vehicle altitude in the driving interval by his/her intention but cannot select the altitudes at the interval start and end points. In this case, the potential energy change amount can be regarded as a feature quantity in which the situations of the drive path as necessity of climbing are reflected. 
     Alternately, to reflect the situations of a driving road such as a traffic jam of a driving road, for example, average vehicle speed, average distance to a forward vehicle, and the like may be used as the driving environment variable. An energy change amount obtained by adding the kinetic energy change amount and the potential energy change amount may be used as the driving environment variable. 
       FIG. 8  shows an example calculation of the driving environment variable more concretely. In the example, the vehicle speed, vehicle weight, and vehicle altitude at the interval start point are calculated as v 1 , m, and h 1 , respectively. The vehicle speed, vehicle weight, and vehicle altitude at the interval end point are calculated as v 2 , m, and h 2 , respectively. Time sequence of driving road resistance  802  is also calculated. The values of driving environment variables, specifically, driving road resistance average X 1  and energy change amount X 2  are calculated as 2.2 and 2.4, respectively. 
     Referring again to  FIG. 1 , the distribution function selector  106  selects a distribution function (probability density function) corresponding to the driving environment variables stored in the driving environment variable storing unit  105  from function set stored in the function set storing unit  107 . The selected distribution function is stored in the distribution function storing unit  108 . 
       FIG. 9  shows an example of selecting a distribution function  901  from the function set. From the function set which are arranged in a lattice shape, a distribution function  901  corresponding to the driving environment variables (X 1 , X 2 )=(2.2, 2.4) is selected. 
     The distribution functions are obtained from actual driving of various drivers including a skilled driver and an inexperienced driver on various driving roads. The distribution function shows a probability density function for obtaining the probability of fuel consumption rate from the fuel consumption rate. 
     When the probability density function are integrated in the total range, 1 is obtained. The distribution function corresponding to the driving environment variable indicative of a downhill may be a narrow distribution because the influence on the fuel consumption of the driving skill is small. On the other hand, a distribution function corresponding to the driving environment variable indicative of an uphill may be a wide distribution because the fuel consumption largely fluctuates depending on the driving skill. In place of the probability density function, a cumulative distribution function may be also used. The probability density function and the cumulative distribution function have the relation that an integral of probability density function matches a cumulative distribution function. The cumulative distribution function increases from 0 to 1 as a probability variable increases. 
     Referring again to  FIG. 1 , the fuel consumption rate evaluator  109  evaluates the driving result by using the interval fuel information (M, Fa, Fk, and F) stored in the interval fuel information storing unit  103  and distribution function stored in the distribution function storing unit  108  and stores the evaluation result into the evaluation value storing unit  110 . The fuel consumption rate evaluator  109  will be described more specifically. 
       FIG. 10  is a configuration diagram of the fuel consumption rate evaluator  109 . As shown in  FIG. 10 , the fuel consumption rate evaluator  109  has reference probability holder  1001 , reference fuel consumption rate calculator  1002 , reference fuel consumption rate storing unit  1003 , and fuel loss calculator  1004 . 
     In the reference probability holder  1001 , a reference probability as a value in which a target level of driving is reflected is stored. For example, reference probability of 0.7 is stored. 
     The reference fuel consumption rate calculator  1002  calculates reference fuel consumption rate so that a value obtained by integrating the distribution function from 0 to the reference fuel consumption rate becomes the reference probability by using the distribution function stored in the distribution function storing unit  108 . The calculated reference fuel consumption rate is stored into the reference fuel consumption rate storing unit  1003 . 
       FIG. 11  shows an example calculation of the reference fuel consumption rate. In the example, the fuel consumption rate 6.4 corresponding to the reference probability 0.7 is calculated as reference fuel consumption rate Mb. That is, a result (area) of integrating the distribution function  901  from 0 to 6.4 is 0.7. If actual fuel consumption rate M is 6.0, it can be considered that there is a fuel loss of 0.4 with respect to the target fuel consumption level (6.4). 
     The fuel loss calculator  1004  calculates a fuel loss in the driving interval by using the interval fuel information (M, Fa, Fk, and F) stored in the interval fuel information storing unit  103  and the reference fuel consumption rate stored in the reference fuel consumption rate storing unit  1003 . The calculated fuel loss is stored as an interval evaluation value into the evaluation value storing unit  110 . 
       FIG. 12  shows an example of the interval evaluation value calculated from the interval fuel information (M, Fa, Fk, and F) in  FIG. 4  and the reference fuel consumption rate Mb in  FIG. 11 . A fuel loss 0.028 by driving in the driving interval shown in  FIG. 12  is calculated by the following equation.
 
( F−Fa−Fk )*( Mb−M )/ Mb≈ 0.028 [l] 
 
From the fuel loss, the driving skill can be purely evaluated.
 
       FIG. 12  shows, in addition to the fuel loss by driving, a fuel loss Fa (=0.1) by idling, a fuel loss Fk (=0.05) by racing, and a total fuel loss (=0.028+0.1+0.05) obtained by adding all of the losses. 
     By feeding back the evaluation result in which situations of various driving roads are reflected to the driver, the driver can recognize the result of his/her driving in a real time. 
     Referring again to  FIG. 1 , the distribution function updater  111  updates a distribution function in the function set storing unit  107 , corresponding to the driving environment variable stored in the driving environment variable storing unit  105  by using the interval fuel information stored in the interval fuel information storing unit  103 . 
       FIG. 13  shows an example of updating of a distribution function. When it is assumed that fuel consumption rate M as a value larger than an average occurs in the distribution function, updating is performed to shift an original distribution function  1301  to the right, thereby obtaining a distribution function  1302 . Concretely, updating is performed by using, for example, maximum likelihood estimation, Bayesian estimation, and the like. By such updating, a distribution function in which the driving skill level of the driver and the driving skill level of a driver group sharing the function set are properly reflected can be obtained by learning. 
     The processes performed by the driving evaluation apparatus can be also realized by causing a computer to execute a program. 
     The components shown in  FIG. 1  may be disposed in the same apparatus or disposed separately in different apparatuses. For example, the components  101  to  105  are disposed in an apparatus in a vehicle to be evaluated, and the components  106  to  111  are disposed in an apparatus mounted in a data center or the like. In this case, the data in the interval fuel information storing unit  103  and the driving environment variable storing unit  105  is transmitted from the apparatus in the vehicle to the apparatus mounted in the data center or the like. The apparatus mounted in the data center or the like evaluates the driving result on the basis of the data received from the apparatus in the vehicle. 
     As described above, according to the embodiment, a distribution function according to the present driving environments is selected from the function set, and the driving result is evaluated on the basis of the selected distribution function. Therefore, the driving result can be evaluated while properly reflecting the driving environments without depending on domain knowledge. 
     According to the embodiment, the distribution function is updated by using the driving environment variables and interval fuel information obtained from actual driving of drivers. Consequently, the distribution function matching the level of the driving skill of the driver and the level of the driving skill of the driver group sharing the function set can be obtained by learning, and the driving result can be effectively evaluated. 
     According to the embodiment, in the driving interval, average of driving road resistance which continues to be exerted to a vehicle irrespective of driving skill during a driving is calculated, and the calculated value is used as the driving environment variable. Therefore, driving can be evaluated while reflecting resistance out of relation to the skill of a driver. 
     According to the embodiment, change in the kinetic energy in the driving interval is calculated, and the calculated value (kinetic energy change amount) is used as a driving environment variable. Thus, evaluation of driving in which the driving environments of necessity of acceleration are reflected can be made. 
     Specifically, when the speeds at the start and end points in the driving interval are regarded as regulations which cannot be selected by the driver, in a driving interval where a vehicle has to be accelerated, the driving environments are regarded as bad from the viewpoint of fuel consumption rate. In a driving interval where a vehicle has to be decelerated, the driving environments are regarded as good. In the embodiment, the driving result can be evaluated while properly considering the situations. 
     According to the embodiment, change in the potential energy in the driving interval is calculated, and the calculated value (potential energy change amount) is used as a driving environment variable. Consequently, efficiency of driving in which the driving environment such as necessity of climbing is reflected can be evaluated. 
     Specifically, when the altitudes at the start and end points in the driving interval are regarded as regulations which cannot be selected by the driver, in a driving interval where the vehicle has to climb a hill, driving environments are regarded as bad from the viewpoint of fuel consumption rate. In a driving interval where a vehicle drives on a downhill, the driving environments are regarded as good. In the embodiment, the driving result can be evaluated while properly considering the situations. 
     According to the embodiment, the distance between the target vehicle and a forward vehicle in the driving interval is calculated, and average distance between vehicles is used as the driving environment variable. Consequently, the driving result can be evaluated while properly reflecting the driving environments such as a traffic jam state of a driving road. 
     Specifically, the average distance between vehicles approximately reflects the traffic jam state of the driving road. The state where traffic jam occurs is regarded as a bad driving environment from the viewpoint of fuel consumption rate. In the embodiment, by using the average distance between vehicles as the driving environment variable, the driving result can be evaluated while properly considering the traffic jam state of the driving road. 
     According to the embodiment, fuel consumption rate based on a fuel consumption amount excluding an amount of fuel consumed by racing and excessive idling which are regarded inefficient in any driving environments is evaluated. Consequently, the driving skill can be purely evaluated. 
     According to the embodiment, the difference between the fuel consumption amount corresponding to given reference probability and actual fuel consumption amount is calculated. Therefore, a fuel loss in the current interval can be fed back to the driver. 
     For example, when the reference probability is set to 0.5, by comparing expected fuel consumption amount in the case of driving with an average skill with actual fuel consumption amount, a fuel loss with respect to the average level in the current interval can be fed back to the driver. By fixing the reference probability, evaluation can be made on the basis of the consistent driving skill level irrespective of the driving environments. 
     According to the embodiment, a total fuel loss amount is calculated by adding the difference between fuel consumption amount by actual normal driving (which does not include racing and idling) and reference fuel consumption amount without racing and idling (fuel loss caused according to pure driving skill) and the amount of a fuel loss caused by racing and excessive idling which is regarded inefficient in any driving environments. Therefore, the driving result in which factors other than the pure driving skill are taken into account can be fed back to the driver more properly.