JP5110053B2 - Probe information processing apparatus and computer program - Google Patents

Description

  The present invention relates to a probe information processing apparatus that performs processing for obtaining the passage start time of a link using the position and time of a vehicle included in probe information, and a computer program for causing a computer to execute the processing.

As an intelligent transport system (ITS: Intelligent Transport Systems) promoted by the National Police Agency, there is a new traffic management system (UTMS: Universal Traffic Management Systems) using an optical beacon as a key device.
In such a system, profile control with higher real-time characteristics is employed by optimizing the blue time using future prediction information for signal control. The characteristics of this profile control are as follows (see Non-Patent Document 1).

(1) Predicting future one-cycle traffic demand from now (2) Realization of real-time control based on direct evaluation of vehicle time delay (3) Distributed control decision-making: hybrid type or adjacent intersection in conjunction with central control Autonomous control mode that works with emphasis can be selected

In the profile control described above, an arrival profile, which is time-series data of the predicted traffic volume at which the vehicle arrives at the stop line at the intersection, is estimated every predetermined time, and a simulation calculation is performed based on this arrival profile and other signal control information. Run.
Specifically, this simulation calculation obtains a delay time (signal stop waiting time) that is a fluctuation state of the number of queues in the entire intersection, searches for a blue end timing at which the evaluation value based on this delay time is minimized, The optimum blue end timing is determined (see Non-Patent Document 1).

Moreover, in the central device of the traffic control center, as a subsystem of the UTMS, a traffic information providing system (AMIS), a public vehicle priority system (PTPS), a vehicle operation management system (MOCS), a dynamic route guidance system (DRGS), In some cases, a traffic pollution reduction system (EPMS) or the like is executed.
Among these subsystems, when a vehicle operation management system (MOCS) or a dynamic route guidance system (DRGS) is performed, travel time and a travel route are required as traffic indexes.

"Development and Demonstration Experiment of Next Generation Signal Control System" SEI Technical Review No. 166, March 2004, pages 51-55

The above travel time and travel route are usually estimated using roadside measurement information from roadside sensors consisting of vehicle detectors, image sensors, etc., but if the spatial density of roadside sensors on the infrastructure side is rough, link Travel time and travel route accuracy cannot be improved much.
Therefore, probe information is acquired from a probe vehicle traveling on a road, for example, through an optical beacon, and link travel time and travel route estimation accuracy are obtained using trajectory information including the position and time of the vehicle included in the probe information. May be improved.

The link travel time estimation method using the trajectory information included in the probe information usually calculates the distribution time in which the difference in passing time between the two points is allocated by the distance ratio of each link between the two points. Then, the passage time of the start / end of the link (node) is calculated based on the allocated time, and the difference between the passage times of the start / end is estimated as the link travel time.
However, if the passage time difference between the two previous points included in the probe information is simply allocated by the distance ratio of each link, if there is a difference in the congestion degree of each link between the two points, the distribution Time may be far from actual.

Therefore, in this case, a large error far from the actual time also occurs in the passage time at the start and end of the link, and the estimation accuracy of the link travel time deteriorates.
In view of such circumstances, an object of the present invention is to provide a probe information processing apparatus and the like that can improve the estimation accuracy of a link travel time based on probe information.

  (1) The probe information processing apparatus according to the present invention is a probe information processing apparatus that obtains the passage time at the start and end of a link using the position and time of the vehicle included in the probe information, and is included in the probe information. Based on the position and time of the two previous points, the determination means for determining whether or not the two points are on the same link, and when the two points are not on the same link, estimated from roadside measurement information Calculation means for calculating the passage time of the start and end of the link between the two points using a time obtained by allocating the passage time difference between the two points based on the estimated travel time of the link. It is characterized by being.

According to the probe information processing apparatus of the present invention, when the two points included in the probe information are not on the same link, the calculation unit determines both points based on the estimated travel time of the link estimated from the roadside measurement information. The passage time at the start and end of the link between the two points is calculated using the time allocated to the difference in passage time between the two points, so even if there is a difference in the congestion degree of each link between the two points, the start and end of the link The passing time at the end is not far from the actual.
Therefore, the passage time at the start and end of each link can be calculated with higher accuracy and the accuracy of estimating the link travel time based on the probe information can be improved compared to the case where the difference in passage time between the two points is distributed only by the distance ratio of each link. be able to.

(2) In the probe information processing apparatus of the present invention, when both points included in the probe information coincide with the start and end of the links, the estimated travel based on the roadside measurement information for all the links between the two points The time can be used as it is, but if either or both of the points do not match the start and end of the link, the estimated travel time cannot be used as it is for the link divided internally by that point. .
Therefore, the determination means determines whether or not one or both of the two points coincides with the start and end of the link, and if the determination result does not match, the next partial travel time is determined. It is preferable to distribute the passage time difference between the two points on the basis.

That is, when the determination result is inconsistent, the calculation means calculates the partial travel time by dividing the estimated travel time of the link internally divided by the point by the internal ratio of the link, The passage time difference between the two points is distributed based on the partial travel time.
By performing the distribution based on the partial travel time, the passage time of the link start / end can be calculated even when one or both of the points do not coincide with the link start / end.

(3) In the probe information processing apparatus of the present invention, depending on the state of collecting estimated travel time data, some links between the two points may not have the estimated travel time.
In such a case, the calculation means distributes the passage time difference between the two points based on the distance ratio between the link having the estimated travel time and the link not having the estimated travel time. It is preferable to perform distribution based on the time ratio between the links having the estimated travel time.

  In this case, even if some links do not have estimated travel time, the links that have the remaining estimated travel time are allocated based on the time ratio of the estimated travel time. Compared with the case of allocating only by the link distance ratio, the passage time of the start and end of each link can be calculated with high accuracy.

(4) The probe information processing apparatus of the present invention further includes data adding means for adding the start and end of the link and the calculated passage time corresponding thereto to a probe database that accumulates the probe information. It is preferable.
In this case, the data adding means adds the start and end of the link and the calculated passage time corresponding thereto to the probe database, so that a database that facilitates the link travel time calculation process can be obtained.

  (5) The computer program of the present invention is a computer program for causing a computer to execute processing by the probe information processing apparatus of the present invention, and has the same effects as the probe information processing apparatus of the present invention.

  As described above, according to the present invention, based on the estimated travel time of the link estimated from the roadside measurement information, the passage time difference between the two points included in the probe information is distributed between the two points. Since the calculation accuracy of the passage time at the start and end of the link is improved, the estimation accuracy of the link travel time based on the probe information can be increased.

It is a road top view which shows the traffic control system which can apply this invention. It is a table | surface which shows the relationship of the application of traffic control, a traffic parameter | index, and probe information. It is a functional block diagram which shows the internal structure of a central apparatus. It is a functional block diagram which shows the internal structure of a vehicle-mounted apparatus. It is a graph which shows the determination method of a stop event. It is a road top view which shows the example of a direction change event. It is a table | surface which shows the frame format of probe information. It is a table | surface which shows bit allocation of the various information described in probe information. It is a connection diagram of a link for showing time calculation processing by a central unit. It is a connection diagram of a link for showing another time calculation processing by a central unit. It is a data table in order to show the probe data processing by a central apparatus. It is a connection diagram of a link in order to show probe data processing by a central unit.

[Overall system configuration]
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a road plan view showing an example of a traffic control system to which the present invention can be applied.
As shown in FIG. 1, the traffic control system of the present embodiment includes a traffic signal 1, a vehicle-mounted device 2, a roadside sensor 3 including a vehicle detector, a central device 4, and a probe vehicle 5 (hereinafter referred to as a vehicle-mounted device 2). It may be simply referred to as a vehicle 5), and an optical beacon 6 or the like.

Among these, the traffic signal 1 is composed of four signal lamps 1b installed on the main roads RM1, RM2 and subways RS1, RS2, respectively, and a traffic signal controller 1a connected to the signal lamp 1b via a communication line. And.
The traffic signal controller 1a is connected to a central device 4 in the traffic control center via a communication line such as a telephone line, and the central device 4 is a traffic signal controller at each intersection C in its own jurisdiction area. 1a and a local area network (LAN).

Accordingly, the central device 4 can perform bidirectional communication with the traffic signal controller 1a, and the traffic signal controller 1a can also perform bidirectional communication with the controller 1a at other intersections. The central device 4 may be installed on the road instead of the traffic control center.
The traffic signal controller 1a receives a signal control command S1, which is an output resulting from traffic sensitivity control such as MODERATO (Management by Origin-Destination Related Adaptation for Traffic Optimization) control, from the central device 4, and performs this signal control. Based on the command S1, lighting, extinguishing and blinking of the signal lamp included in each signal lamp 1b are controlled.

The traffic signal controller 1 a is also connected to the optical beacon 6 through a communication line, and transmits traffic information S 2 including traffic information and travel time received from the central device 4 to the optical beacon 6.
The optical beacon 6 can perform two-way communication with an optical signal with the probe vehicle 5 on which the in-vehicle device 2 is mounted, and transmits the traffic information S2 included in the downlink DL. The uplink UL transmitted from the in-vehicle device 2 to the optical beacon 6 includes probe information S3 described later. The probe information S3 is transferred to the central device 4 via the traffic signal controller 1a together with the uplink UL reception time and beacon ID.

The roadside sensor 3 measures, for example, a vehicle detector that ultrasonically senses a vehicle passing underneath, a loop coil that senses the vehicle by inductance change, or image processing of a camera image to measure traffic volume and vehicle speed. It consists of image sensors and is installed on some roads in the jurisdiction area for the purpose of measuring the number of vehicles flowing into the intersection C and the vehicle speed.
The roadside measurement information S4 detected by the roadside sensor 3 is relayed by the traffic signal controller 1a and transmitted to the central apparatus 4 via the communication line.

[Central equipment]
FIG. 3 is a functional block diagram showing the internal configuration of the central device 4.
As illustrated in FIG. 3, the central device 4 includes a control unit 401, a display unit 402, a communication unit 403, a storage unit 404, and an operation unit 405.
The control unit 401 of the central device 4 includes a workstation (WS), a personal computer (PC), etc., and collects / processes (calculates) / records various traffic information from the traffic signal controller 1a, controls signals, and provides information. Is performed in an integrated manner. Note that the control unit 401 of the central device 4 is connected to the hardware units via an internal bus, and also controls the operations of these units.

The control unit 401 of the central device 4 controls the traffic signal controller 1a belonging to its own jurisdiction area by adjusting the traffic signal group 1 on the same road, or wide-area control that extends this system control to the road network. (Surface control) can be executed.
That is, the control unit 401 of the central device 4 performs traffic sensitive control for setting signal control parameters (split, cycle length, offset, etc.) according to traffic conditions. For example, a plurality of types including the MODERATO control and the profile control are included.

The communication unit 403 of the central device 4 is a communication interface connected to the LAN side via a communication line, and includes a signal control command S1 relating to the timing of switching the color of the signal lamp 1b every predetermined time, and the travel time of the road link. Traffic information S2 including traffic information and traffic information is transmitted to each traffic signal 1.
The signal control command S1 is transmitted every signal control parameter calculation cycle (for example, 1.0 to 2.5 minutes), and the traffic information S2 is transmitted every five minutes, for example.

  In addition, the communication unit 403 of the central device 4 performs traffic signal control on the probe information S3 that is movement measurement information including the position and time (trajectory) of the probe vehicle 5 and the vehicle ID, and roadside measurement information S4 by the roadside sensor 3. From the device 1a.

The display unit 402 of the central device 4 includes a road map of an area managed by the central device 4 and a display screen on which positions of all traffic signals 1, roadside sensors 3, and optical beacons 6 are displayed on the road map. It informs the central operator of traffic conditions such as traffic jams and accidents.
The operation unit 405 of the central device 4 includes an input interface such as a keyboard and a mouse. The operation unit 405 allows the central operator to perform a display switching operation on the display unit 402.

The storage unit 404 of the central device 4 includes a hard disk, a semiconductor memory, and the like, and stores a control program for the above-described traffic sensitivity control and a calculation program for a traffic index used for the traffic sensitivity control. It also has a temporary storage area for the signal control command S1 and traffic information S2 generated by the unit 401.
The storage unit 404 of the central device 4 includes a probe database DB1, a roadside database DB2, and a map database DB3.

The probe database DB1 accumulates various measurement values (passage position and time of the probe vehicle 5 and its event type, etc.) included in the probe information S3, and the passage time at the link start and end estimated from the measurement values. ing.
In the roadside database DB2, various measurement values of the roadside measurement information S4 (the number of passing vehicles with respect to the vehicle link, etc.) are accumulated.

The road map data in the map database DB3 includes intersection data in which intersection IDs are associated with intersection positions.
The road map data includes the link ID, the link start point / end point / interpolation point (corresponding to the point where the road bends), the link ID of the link connected to the link start point, and the link end point. Link data that associates the link ID of the link to be connected is also included.

Based on the roadside measurement information S4 accumulated in the roadside database DB2, the control unit 401 of the central device 4 calculates the estimated travel time of each link for every predetermined time, and records this estimated value in the map database DB3.
Instead of the central device 4 itself estimating the estimated travel time of each link based on the roadside measurement information S4 from the roadside sensor 3, each link from a traffic information distribution center such as a VICS center ("VICS" is a registered trademark) is used. The estimated travel time (ie, “VICS travel time”) may be acquired.

  In addition, the estimated travel time of each link is usually a past estimated value that is updated every 5 minutes based on the latest roadside measurement information S4. It may be a predicted value of travel time of each link for the future obtained using a prediction algorithm.

  The control unit 401 of the central device 4 according to the present embodiment uses the position and time of the probe vehicle 5 included in the probe information S3 and the estimated travel time to obtain the passage time at the start and end of the link “time calculation process” Then, “probe data processing” for adding the passage time and other data to the probe information S3 is performed. Details of these processes will be described later.

[Types of traffic control by central equipment]
FIG. 2 is a table showing the relationship between the traffic control application executed by the control unit 401 of the central apparatus 4, the traffic index that is input information necessary for the application, and the probe information necessary for calculating the traffic index. It is.
For example, the traffic indicators (input information for traffic control) necessary for MODERATO control and profile control implemented for the advancement of signal control are the number of queues and saturated traffic flow rate, which are necessary for detour priority control. Traffic indicators are travel time and travel route.

The traffic index necessary for detecting the bottleneck position, which is implemented for the traffic flow analysis, is the number of stops of the vehicle 5 that is running.
Furthermore, the estimation of CO2 emissions performed by MOCS requires the number of stops of vehicle 5 (in this case, it is necessary to distinguish between repeated stop and single stop described later). The traffic index necessary for management is the travel route of the vehicle 5.

[In-vehicle device]
FIG. 4 is a functional block diagram showing the internal configuration of the in-vehicle device 2 of the probe vehicle 5.
The in-vehicle device 2 has a road-to-vehicle communication function that performs bidirectional optical communication with the optical beacon 6 and a navigation function that guides the destination set by the passenger.
As shown in FIG. 4, the in-vehicle device 2 includes a GPS processing unit 201, a direction sensor 202, a vehicle speed acquisition unit 203, an optical communication unit 204, a storage unit 205, an operation unit 206, a display unit 207, an audio output unit 208, and a control unit. 209 etc.

The GPS processing unit 201 receives GPS signals from GPS satellites, and determines the position (latitude, longitude, and altitude) of the probe vehicle 5 based on time information, GPS satellite orbits, positioning correction information, and the like included in the GPS signals. measure.
The direction sensor 202 is constituted by an optical fiber gyro or the like, and measures the direction and angular velocity of the probe vehicle 5. The vehicle speed acquisition unit 203 acquires speed data of the probe vehicle 5 measured by a vehicle speed sensor (not shown) detecting the angular speed of the wheels.

The optical communication unit 204 of the in-vehicle device 2 transmits and receives the uplink UL and the downlink DL in the communication area of the optical beacon 6 set at a predetermined position on the road. That is, when the probe vehicle 5 that has flowed out of the intersection C enters the communication area of the optical beacon 6, the optical communication unit 204 of the in-vehicle device 2 receives the downlink DL including the traffic information S2 and includes its own probe information S3. The uplink UL is transmitted to the optical beacon 6.
The storage unit 205 of the in-vehicle device 2 includes a hard disk, a semiconductor memory, and the like, and has a storage area for storing various information such as traffic information S2 included in the downlink DL and probe information S3 included in the uplink UL. .

The storage unit 205 also stores road map data.
This road map data includes intersection data in which intersection IDs are associated with intersection positions. In the road map data, the link ID, the link start point / end point / interpolation point (corresponding to the point where the road bends), the link ID of the link connected to the link start point, and the link end point are connected. Link data in which the link ID of the link to be associated with the link cost used for specifying the optimum route is also included.

For example, the number of link costs is the same as the number of links and links connected to the end point, and after entering the start point of the link, the end point of the link is exited, and the start point of the next link to be connected is entered. The time required to do is set.
That is, the link cost includes the cost (time) required to travel from the start point to the end point of the link and the cost (time) required to travel from the end point of the link to the start point of the next link, that is, the intersection. The cost required to pass is included.

The operation unit 206 of the in-vehicle device 2 includes a touch panel, buttons, and the like, and a passenger of the vehicle 5 including a driver can set a destination.
The display unit 207 of the in-vehicle device 2 includes a monitor device (not shown) attached to the dashboard portion of the vehicle 5, and displays image data created by the control unit 209 in the sensitivity request process described later to the passenger. The audio output unit 208 outputs the audio data created by the control unit 209 from a speaker (not shown).

The control unit 209 of the in-vehicle device 2 includes a microcomputer or the like, and includes a GPS processing unit 201, a direction sensor 202, a vehicle speed acquisition unit 203, an optical communication unit 204, a storage unit 205, an operation unit 206, a display unit 207, and an audio output unit. Each process in 208 is controlled.
In addition, the control unit 209 of the in-vehicle device 2 includes data on the position of the vehicle 5 measured by the GPS processing unit 201, the azimuth and angular velocity of the vehicle 5 measured by the orientation sensor 202, and the speed of the vehicle 5 acquired by the vehicle speed acquisition unit 203. The map matching process is performed based on the road map data stored in the storage unit 205, and the position of the probe vehicle 5 on the link of the road map data can be calculated.

  Furthermore, in the storage unit 205 of the in-vehicle device 2, “event determination processing” for determining the occurrence of various events that occur during the traveling of the probe vehicle 5, and the event and its relation according to the nature of the various events. A computer program for determining which information to include in the probe information S3 and causing the control unit 209 to execute an “information generation process” for generating the probe information S3 for each event is stored. .

The control unit 209 of the in-vehicle device 2 executes the “event determination process” and the “information generation process” by reading the program from the storage unit 205 and executing the program. Hereinafter, these processes which the control part 209 of the vehicle-mounted apparatus 2 performs are demonstrated.
In the present embodiment, since the optical beacon 6 is used as a means for transmitting the probe information S3 to the infrastructure side, the control unit 209 of the in-vehicle device 2 causes the optical beacon 6 to pass next to the optical beacon 6. Probe information S3 describing various events that occurred during traveling on the route between the two and related information is generated.

[Content of processing related to stop event]
The stop events determined by the control unit 209 of the present embodiment include “independent stop” and “repetitive stop”.
FIG. 5 is a graph showing a method for determining a stop event between the single stop and the repeated stop. In the graph of FIG. 5, the horizontal axis is the travel distance of the vehicle 5, and the vertical axis is the speed.
Further, the first threshold value V1 in FIG. 5 is a threshold value for determining whether the stop of the vehicle 5 is repeated stop or single stop, and is set to 30 km / h, for example. The second threshold value V2 is a value that can be regarded as a substantial stop when the speed is less than this, and is set to, for example, 5 km / h.

Here, “independent stop” refers to a stop after the vehicle 5 reaches a speed equal to or higher than a certain speed, and is an event assuming that the vehicle 5 stops due to waiting for a signal or reaching the end of a traffic jam. It is. “Repeated stop” means that the vehicle stops again before reaching a certain speed from the previous stop, and is an event that assumes that the vehicle 5 repeatedly stops and starts due to traffic jams (Stop & Go). is there.
For example, as indicated by points A and B in FIG. 5, the speed of the vehicle 5 monotonously decreases from a state where it exceeds the first threshold value V1, the speed falls below the second threshold value V2, and the vehicle 5 stops. If it is determined, it is determined to be a single stop.

On the other hand, as indicated by point C in FIG. 5, after the speed of the vehicle 5 has increased or decreased within the range less than the first threshold value V1, it is determined that the vehicle 5 has stopped because the speed has fallen below the second threshold value V2. If it is, it is determined that the repetition is stopped. Under the above determination conditions, the control unit 209 of the in-vehicle device 2 executes the following processes (1) to (6).
(1) First, the control unit 209 clears all of the number of repeated stops, the number of independent stops, the restart time and stop position, and the high-speed traveling flag at the time of activation.

(2) Next, the control unit 209 monitors the speed of the vehicle 5 every predetermined time (for example, 1 second) set in advance, and if this speed is equal to or higher than the first threshold value V1, the high-speed running flag Set to on.
(3) Next, the control unit 209 determines that the vehicle 5 has stopped when the state where the speed is less than the second threshold value V2 continues for a certain number of seconds (constant setting: for example, 5 seconds).

In this case, when the high-speed traveling flag is on, the vehicle 5 can be regarded as being in the state of point A or point B in FIG. 5, so the number of independent stops is incremented, and when the high-speed flag is off, Since it can also be in the state of point C, the number of repeated stops is incremented.
(4) Further, after determining that the vehicle 5 is stopped, the control unit 209 determines that the vehicle 5 has restarted when the speed exceeds the second threshold value V2. At this time, if the high-speed running flag is on, it corresponds to the case of single stop, so that the restart time, stop position, and stop time are stored in the storage unit 205.

However, the control unit 209 previously sets a limited number (constant setting: for example, 3 times) that can be included in the probe information S3 for the single stop event with the stop position. Therefore, when the number of single stops from the previous uplink UL exceeds the above-mentioned limited number, the control unit 209 overwrites the oldest data and updates the restart time, stop position, and stop time of the single stop. To do. In addition, the control unit 209 finally sets the high speed travel flag to OFF.
(5) The control unit 209 repeats the processes (2) to (4) until communication with the next optical beacon 6 occurs.

(6) Further, the control unit 209 performs generation processing of probe information S3 including the following event information (a) until communication with the next optical beacon 6 occurs, and at the time of passing, the probe information S3 Are included in the uplink UL and transmitted to the optical communication unit 204.
(A) Single stop event information-Stop position, restart time and stop time-Number of repeated stops that occurred before the single stop from the previous uplink event-Before the single stop from the previous uplink event Number of independent stops that occurred and are no longer uplink events due to data updates

Here, the “uplink event” is an event included in the probe information S3 as an event having at least position information. In addition to the single stop event of (a) having a stop position, This includes events of constant distance travel.
Note that after the transmission of the uplink UL to the optical beacon 6, the control unit 209 clears all the stop position, the restart time, and the stop time that constitute the single stop event information as the uplink event.

As described above, when the stop event is a single stop, the control unit 209 includes the stop position, the restart time, and the stop time in the probe information S3 for those within a predetermined limited number (for example, three times). However, the stop position, the restart time, and the stop time are not included in the probe information S3 for the single stop whose data has been updated because the limit number has been exceeded and for all repeated stops.
However, the number of single stop and repeated stop is included in the probe information S3 as event information associated with the next uplink event.

  According to the in-vehicle device 2 of the present embodiment, the control unit 209 determines a single stop caused by waiting for a signal or the like and a repeated stop that repeats the stop and start as separate events, and the number of queues and the saturated traffic flow rate For the single stop required for the calculation of the number of events, the information below the predetermined limited number includes the stop position, restart time and stop time as event information. Included in the information.

Accordingly, it is possible to generate the probe information S3 that can calculate the traffic index such as the number of queues and the saturated traffic flow rate while efficiently using the data amount for storing and transmitting the probe information S3.
In addition, since the number of stops is included in the event information of each uplink event so that it is possible to distinguish between a single stop and a repeated stop, the central device 4 that has acquired the probe information S3 from the in-vehicle device 2 Using the number of stops included in the link event, it is possible to estimate the CO2 emission amount by MOCS.

[Content of processing related to direction change events]
FIG. 6 is a road plan view showing an example of a direction change event.
FIG. 6A shows a direction change event that occurs on a right turn at an intersection (however, a left turn may be used), and FIG. 6B shows a direction change event that occurs on a relatively sharply curved single road. .
The control unit 209 of the in-vehicle device 2 extracts “direction fluctuation” having a small curvature radius and a large change in the traveling direction of the vehicle 5 as an event as shown in FIG. 6, and generates probe information S3 related thereto. The following processes (1) to (5) are executed.

(1) First, the control unit 209 monitors the traveling locus of the vehicle 2 every certain time (constant setting: for example 1 second), and the vehicle 5 is constant from the previous locus stored in the storage unit 205 last time. If the vehicle travels more than a distance (constant setting: 10 m, for example), the storage unit 205 stores the position (latitude and longitude) and direction (if not found from the relative position with respect to the previous time) as the current locus.
(2) Next, if the azimuth difference between the previous trajectory and the current trajectory is equal to or greater than a certain value (constant setting: 5 degrees, for example), the control unit 209 regards that the azimuth change has started.

(3) Furthermore, the control unit 209 determines that the azimuth difference between the previous trajectory and the current trajectory is less than a certain value (constant setting: for example, 5 degrees) and the number of times is constant (constant setting: for example, twice). The direction change is considered complete.
(4) Next, if the difference between the azimuth at the start of the azimuth change and the azimuth at the end of the azimuth change is equal to or greater than a certain value (constant setting: 30 degrees, for example), the control unit 209 It is considered that an event has occurred, and the storage unit 205 stores the time, position, and direction at the end of the direction change.

However, the control unit 209 previously sets a limited number (constant setting: for example, twice) that can be included in the probe information S3 for the direction change event and the fixed distance travel event described later, separately from the single stop. is doing.
Therefore, if the total number of those events from the previous uplink UL exceeds the limited number, the control unit 209 overwrites the oldest data and ends the direction change end time, end position, and absolute direction. To clear.
(5) The control unit 209 repeats the processes (1) to (4) until communication with the next optical beacon 6 occurs.

(6) Further, the control unit 209 performs generation processing of the probe information S3 including the following event information (b) until communication with the next optical beacon 6 occurs, and when passing, the probe information S3 Are included in the uplink UL and transmitted to the optical communication unit 204.
(B) Direction change event information-Direction change end time, end position and absolute direction-Number of repetitive stops that occurred before the direction change from the previous uplink event-From the uplink event of the direction change Number of previous single outages that were no longer uplink events due to data updates

  Note that after the transmission of the uplink UL to the optical beacon 6, the control unit 209 clears all the azimuth change end time, end position, and absolute azimuth constituting the direction change event information as the uplink event.

[Contents of processing related to fixed-distance driving events]
The control unit 209 of the in-vehicle device 2 determines whether or not the vehicle 5 has traveled a sufficiently long constant distance (determined distance travel) as an event, and generates probe information S3 related to this, so that the following process (1) Execute (4).

(1) First, the control unit 209 clears the accumulated travel distance when either the stop event (single stop or repeated stop) or the direction change event occurs. The control unit 209 also clears the cumulative travel distance even when a direction change event occurs before the cumulative travel distance exceeds a certain distance (constant setting: for example, 500 m).
(2) Next, the control unit 209 monitors the travel locus every predetermined time (constant setting: for example, 1 second), and integrates the travel distance from the previous event.

(3) If the cumulative travel distance exceeds a certain distance (constant setting: 500 m, for example), the control unit 209 considers that a certain distance travel event has occurred and stores the time, position, and direction in the storage unit 205.
However, as described above, since a limited number (constant setting: for example, 2 times) is set for the total number of directional fluctuations and fixed distance travel, the total number of those events from the previous uplink UL is the limited number. If it exceeds, the oldest data is overwritten and the accumulated mileage is cleared.

  (4) The control unit 209 repeats the processes (1) to (3) until communication with the next optical beacon 6 occurs.

(5) Further, the control unit 209 performs generation processing of probe information S3 including the following event information (c) until communication with the next optical beacon 6 occurs. Are included in the uplink UL and transmitted to the optical communication unit 204.
(C) Event information of constant distance travel ・ End time, position and cumulative travel distance of constant distance travel ・ Number of repeated stops that occurred before the predetermined distance travel from the previous uplink event ・ From the previous uplink event Number of independent stops that occurred before a certain distance and were no longer an uplink event due to data update

  Note that after the transmission of the uplink UL to the optical beacon 6, the control unit 209 clears all the travel end time, position, and cumulative travel distance that constitute the event information of a fixed distance travel as an uplink event. .

[Exception handling for stop events]
By the way, the point P of Fig.6 (a) has shown the stop position in the intersection at the time of a right turn. Here, when there is no preceding vehicle on the right turn lane, the traveling vehicle 5 decelerates to a point P that is less than the second threshold value V2, and a single stop or a repeated stop may occur at the point P.
However, the point P in the intersection is irrelevant to signal waiting, and is not necessary for calculating the number of queues and the saturated traffic flow rate. If this is adopted as a stop event, useless probe information S3 is included. The uplink UL is sent to the infrastructure side.

Therefore, the control unit 209 of the in-vehicle device 2 refers to the road map data included in the storage unit 205, and based on which position in the road map data the traveling position of the vehicle 5 is changing the direction. It is determined whether or not the stop event of the vehicle 5 is a right turn stop that is a stop within an intersection at the time of a right turn as indicated by a point P in FIG. 6 (a). It is not adopted as a single stop or repeated stop.
In other words, the control unit 209 processes the right turn stop as a stop event that is not included in the probe information S3 without being an uplink event.

On the other hand, a point Q in FIG. 6B indicates the stop position of the vehicle 5 during the direction change on a relatively sharp single road. Here, when the signal at the intersection on the downstream side of the single road is red, the traveling vehicle 5 decelerates to a value less than the second threshold value V2 at the point Q, and stops alone or repeatedly at the point Q. May occur.
Therefore, it is considered that the stop at the point Q during the direction change on a single road is necessary for calculating the number of queues and the saturated traffic flow rate, unlike the case of the right turn in FIG. The stop event should be included in the probe information S3.

Therefore, the control unit 209 of the in-vehicle device 2 refers to the road map data included in the storage unit 205, and based on which position in the road map data the traveling position of the vehicle 5 is changing the direction. It is determined whether or not the stop event of the vehicle 5 is a single road stop that is a stop during a change of direction on a single road, as indicated by a point Q in FIG. 6 (a). This is adopted as a single stop or repeated stop.
That is, the control unit 209 processes the single path stop as a stop event included in the probe information S3.

[Frame contents of probe information]
FIG. 7 is a table showing a frame format of the probe information S3 generated by the control unit 209 of the in-vehicle device 2.
As shown in FIG. 7, the data area of the probe information S3 includes a header, basic items, and attribute types, and the header can describe the number of independent stops and the number of repeated stops.

In addition, the basic item includes a position and measurement time description area, the position is described in latitude and longitude, and the measurement time is described in hours, minutes, and seconds.
Further, the attribute item includes an event type and event value description area. In the event type, the type or flag is described, and in the event value, at least one of direction, stop time, and travel distance is described as a value corresponding to the event type.

[Probe information bit assignment]
FIG. 8 is a table showing bit allocation of various information described in the probe information S3.
As shown in FIG. 8, the stop time in the case of a single stop is represented by 8 bits, divided into the case of second and minute by the initial bit value, and the time is represented by the remaining 7 bits. For this reason, the time from 0x01 (1 second) to 0xff (127 minutes) can be allocated in hexadecimal with 1 second as the minimum unit.

Further, the absolute direction in the case of the direction change is assigned as 16 units in the clockwise direction with “1” in the north.
Furthermore, 8 bits are assigned to the travel distance from the previous event in the case of constant distance travel or direction change, and is in units of 5 m. In this case, a travel distance from 0x01 (5 m) to 0xff (1275 m) can be assigned in hexadecimal.

[Time calculation process by central unit]
As described above, in the present embodiment, the control unit 401 of the central device 4 uses the position and time of the probe vehicle 5 included in the probe information S3 and the estimated travel time of the link estimated from the roadside measurement information S4. Then, a “time calculation process” for calculating the passage time at the start and end of the link is performed.
FIG. 9 is a link connection diagram for illustrating the time calculation process. Hereinafter, the contents of the time calculation process will be described with reference to FIG.

In the figure, l (lower-case el) 1 to 13 indicate specific links recorded in the map database DB3 of the central device 4, and the connection points (nodes) are n0 to n3.
In this embodiment, a connection point on the upstream side in the traveling direction (left side in FIG. 9) with respect to a specific link is referred to as a “starting end”, and a connection point on the downstream side in the traveling direction (right side in FIG. 9). Is called “end”. For example, the start end of the link l1 is the node n0, and the end point is the node n1. The start end of the link l2 is the node n1, and the end point is the node n2.

Moreover, in FIG. 9, t1-t3 shows the estimated travel time of each link 11-l3. The estimated travel times t1 to t3 are calculated in advance by the control unit 401 for each of the links 11 to 13 based on the roadside measurement information S4 recorded in the roadside database DB2.
In the example of the figure, as a numerical example, the distances of the links 11 to 13 are all 150 m, and the estimated travel times t1 to t3 of the links are t1 = 100 s (unit of s is second), respectively. t2 = 300 s and t3 = 200 s.

Black triangles (point A and point B) in FIG. 9 indicate an uplink event having a position (coordinate) x and a time i included in the probe information S3. In FIG. X1, i1 and the position and time of the point B are x2, i2.
Further, it is assumed that the passing time difference T (= i2−i1) from the point A to the point B is 400 s, the previous point A is located at the midpoint of the link l1, and the later point B sets the link l3 to 2: Assume that it is located at a point internally divided by three.

For this reason, the distance of the partial link lp1 from the point A to the node n1 in the link l1 is lp1 = 75 m, and the distance of the partial link lp3 from the node n2 to the point B in the link l3 is lp3 = 60 m.
The total distance X traveled from the point A to the point B by the probe vehicle 5 is X = lp1 + l2 + lp3 = 75 + 150 + 60 = 285 m.

Here, the control unit 401 of the central device 4 first determines whether the two points A and B are on the same link based on the position x and the time i of the two previous points A and B included in the probe information S3. Determine whether.
The reason is that two points A. This is because if B is on the same link, there is no need to distribute the passage time difference T between the points A and B to a plurality of links. In the example shown in the drawing, the point A is in the middle of the link l1 and the point B is in the middle of the link l3. Therefore, the determination result of the determination is No (No).

And when both points A and B are not on the same link, the control unit 401 of the central device 4 determines the time based on the estimated travel times t1 to t3 of the links l1 to l3 estimated from the roadside measurement information S4. By allocating the passage time difference T (= 400 s) between the two points A and B according to the ratio, the passage times at the start and end of the links 11 to 13 between the two points A and B are calculated.
In this case, when both points A and B match the start and end of the links 11 to 13 (in FIG. 9, when the point A matches the node n0 and the point B matches the node n3), all the links The estimated travel times t1 to t3 can be used as they are for l1 to l3.

However, in the example of FIG. 9, the point A is at the midpoint of the link l1, and the point B is an internal dividing point that internally divides the link l3 into 2: 3. The estimated travel times t1 and t3 cannot be used as they are.
Therefore, the control unit 401 determines whether or not both the points A and B are coincident with the start and end of the links l1 and l3, and when the determination result is not coincident, Partial travel times tp1 and tp3 obtained by dividing the estimated travel times t1 and t3 by the internal ratio are calculated, and the passage time difference T between the points A and B is distributed based on the partial travel times tp1 and tp3.

  For example, in FIG. 9, since the point A is the midpoint of the link 11 and does not coincide with the start / end of the link 11, the control unit 401 determines the estimated travel time t1 of the link 11 as the internal division of the link 11. By dividing at a ratio of 1: 1, the partial travel time tp1 corresponding to the partial link lp1 from the point A to the end of the link l1 (node n1) is calculated. Therefore, the partial travel time tp1 is tp1 = t1 × (1/2) = 50 s.

Further, the control unit 401 divides the estimated travel time t3 of the link l3 by the internal division ratio 2: 3 of the link l3, thereby corresponding to the partial link lp3 from the start point (node n2) of the link l3 to the point B. The partial travel time tp3 is calculated. Accordingly, the partial travel time tp2 is tp2 = t2 × (2/5) = 80 s.
Next, the control unit 401 uses the time ratio of the partial travel time tp1 (= 50 s) of the link l1, the estimated travel time t2 (= 300s) of the link l2, and the partial travel time tp3 (= 80s) of the link l3, The passage time difference T (= 400) from the point A to the point B is distributed for each of the links 11 to 13.

That is, if the allocation time for the partial link lp1 from the point A to the node n1 is a, the allocation time for the entire link l2 is b, and the allocation time for the partial link lp3 from the node n2 to the point B is c, the control unit 401 These allocation times a to c are calculated as follows.
a = {50 / (50 + 300 + 80)} × 400 = 46.5 (seconds)
b = {300 / (50 + 300 + 80)} × 400 = 279.0 (seconds)
c = {80 / (50 + 300 + 80)} × 400 = 74.5 (seconds)

Thereafter, the control unit 401 calculates the passage times of the start and end of the links 11 to 13 between the two points A and B using the distribution times a to c distributed at the above time ratio.
For example, the control unit 401 calculates the passage time of the node n1 by adding the distribution time a to the passage time i1 of the point A, adds the distribution time b to the passage time of the node n1, and determines the passage time of the node n2. calculate.

On the other hand, as in the prior art, the passage time difference T between the two points A and B is allocated according to the distance ratio of the links 11 to 13 (however, the links 11 and 13 are the partial links 1p1 and 1p3). Then, since lp1 = 75 m, l2 = 150 m, and lp3 = 60 m, the allocation times a ′ to c ′ are calculated as follows.
a ′ = {75 / (75 + 150 + 60)} × 400 = 105.3 (seconds)
b ′ = {150 / (75 + 150 + 60)} × 400 = 210.5 (seconds)
c ′ = {60 / (75 + 150 + 60)} × 400 = 84.2 (seconds)

However, with such a distribution method based on the distance ratio, the distribution time a ′ to c ′ of the passage time difference T obtained from the probe information S3 may be far from the actual, and the link travel time estimation accuracy may deteriorate. The reason is as follows.
That is, in the example shown in FIG. 9, the estimated travel times of the links 11 to 13 having the same distance are t2>t3> t1. For this reason, the actual road congestion level is also estimated to be link l2> link l3> link l1, but in the allocation times a ′ to c ′ based on the distance ratio, the links l1 to l3 Since the degree of congestion is not reflected, the value may be far from the actual value.

For example, focusing on the link l1 in FIG. 9, the distribution time a ′ for the partial link lp1 when the passage time difference T is distributed by the distance ratio is 105.3 s, and this value is an estimate of the entire link l1. The abnormal value is larger than the travel time t1. The reason is that the time that should originally be allocated to the link l2 having a high degree of congestion is excessively allocated to the link l1 side due to the allocation by the distance ratio.
Therefore, when such an abnormal value distribution time a ′ is used, the passage time of the end of the link 11 (node n1) also includes a large error far from the actual, and the estimation accuracy of the link travel time deteriorates. It will be.

On the other hand, in the present embodiment, the passage time difference T from the point A to the point B is distributed according to the time ratio of the travel times tp1, t2, tp3, so the links 11 to 13 are allocated to the distribution times a to c. There is no outlier or large error that depends on the difference in congestion.
For example, in the link l1 of FIG. 9, the allocation time a for the partial link lp1 in which the passage time difference T is allocated at the above time ratio is 46.5 s, and this value is the estimated travel time t1 (= 100 s) of the entire link l1. ) Is a reasonable value.

As described above, according to the central device 4 of the present embodiment, the control unit 401 determines the two points A according to the time ratio of the travel times tp1, t2, and lp3 of the links lp1, l2, and lp3 estimated from the roadside measurement information S4. , B, and the distribution times a to c are used to calculate the passage times at the start and end of the links 11 to 13 between the points A and B. Even when there is a difference in the congestion degree, the passage times of the start and end of the links 11 to 13 are not different from the actual ones.
Therefore, it is possible to accurately calculate the passage times at the start and end of each of the links l1 to l3, and it is possible to improve the estimation accuracy of the link travel time based on the probe information S3.

[Modification of time calculation processing (when there is no estimated travel time for some links)]
FIG. 10 is a link connection diagram for illustrating a modification of the time calculation process.
In the example shown in FIG. 10, it is assumed that there is no estimated travel time t2 for a part of the links 11 to 13 between the two points A and B (link 12 in FIG. 10).
In this case, the control unit 401 of the central device 4 first, between the links l1 and l3 (partial links lp1 and lp3 in the case of FIG. 10) having the estimated travel times t1 and t3 and the link l2 not having the estimated travel times t1 and t3, The passage time difference T between the two points A and B is distributed based on the distance ratio.

In addition, the control unit 401 relies on the estimated travel times t1 and t3 between the partial links lp1 and pl3 of the links l1 and l3 having the estimated travel times t1 and t3 after performing the above allocation. Distribution based on the time ratio of partial travel times tp1 and tp3 is performed.
Specifically, in the case of FIG. 10 in which lp1 = 75 m, l2 = 150 m, lp3 = 60 m, tp1 = 50 s, t2 = no data, and tp3 = 80 s, the control unit 401 follows each allocation time a to c. It is calculated according to the following formula.

a = {(75 + 60) / (75 + 150 + 60)} × 400 × {50 / (50 + 80)} = 72.9 (seconds)
b = {150 / (75 + 150 + 60)} × 400 = 210.5 (seconds)
c = {(75 + 60) / (75 + 150 + 60)} × 400 × {80 / (50 + 80)} = 116.6 (seconds)
And the control part 401 calculates the passage time of the start / end of the links 11-l3 between both the points A and B using the allocation time ac distributed by said distance and time ratio.

  As described above, according to the central device 4 of the present embodiment, even when some of the links l2 do not have the estimated travel time t2, the control unit 401 has the remaining links l1, l3 having the estimated travel times t1, t3. (In FIG. 10, the partial links lp1 and pl3) are allocated based on the time ratio of the travel times tp1 and tp3 estimated from the roadside measurement information S4. Compared with the case of allocating only the distance ratio of the links lp1, l2, and lp3, the passage times of the start and end of each of the links l1 to l3 can be calculated with high accuracy.

[Probe data processing by central unit]
When the control unit 401 of the central device 4 calculates the passage times of the start and end (nodes) of the links 11 to 13 by the time calculation processing, the “probe data processing” is performed to add the passage time and other data to the probe information S3. Do.
FIG. 11 shows an example of a data table stored in the database DB1 for showing the probe data processing, and FIG. 12 is a link connection diagram for showing the probe data processing. The details of the probe data processing will be described below with reference to FIGS.

In the first-stage data table of FIG. 11, the “vehicle ID number” is the ID number of the probe vehicle 5 to which the probe information S3 is uplinked, and the “light beacon reception time” is the probe information S3 from the vehicle 5. This is the reception time at the received optical beacon 6.
The “measurement point number” is a number obtained by numbering the points in each row included in this data table. When one interpolation event is added as described later, this point number is also incremented by one.

In the first-stage data table of FIG. 11, “absolute latitude”, “absolute lightness”, and “altitude” are the position data of the uplink event included in the initial probe information S3, and “measurement point measurement time” is , The passage time corresponding to the position data of the uplink event.
Further, in the data table in the first row, “line segment attribute 1” is the number of independent stops associated with the uplink event, and “line segment attribute 2” is the number of iterative stops associated with the uplink event. is there.

“Point attribute 1” indicates the event type of the uplink event. In the example of FIG. 11, the uplink event on the first line is “direction change”, and the uplink event on the second line is “fixed distance”. It is "running".
Further, “point attribute 2” indicates event information data corresponding to each event type. In the case of “change in direction”, the direction of the vehicle 5 (see FIG. 8) is described, and “running a certain distance” In the case of, the mileage from the previous event is described. Although not shown, in the case of “single stop”, the stop time is described in “point attribute 2”.

Here, the control unit 401 of the central device 4 performs map matching on the position data (absolute latitude, absolute lightness and altitude) described in the first-stage data table, and the position data conforms to UTMS. Convert to link data.
As shown in the second-stage data table in FIG. 11, in this example, the position data of “direction variation” in the first-stage data table has “secondary mesh coordinates” of 35714 and “link number” of 2009. It has been converted to link data. Further, the position data of “running a fixed distance” is converted into link data having “secondary mesh coordinates” of 35714 and “link number” of 2011.

In the second-stage data table of FIG. 11, “1” is described in the “measurement point flag” when the measurement point of the event is the in-vehicle device 2, and “0” when the event is the central device 4. be written. Therefore, in the case of an interpolation event added to the data table, the “measurement point flag” is “0”.
The “start / end flag” indicates the type of the start or end of the event. “1” is described for the start end, and “2” is described for the end end.

In the data table in the second row, the “direction change” on the first line occurs in the link with the link number “2009”, and the “run for a fixed distance” on the second line has the link number “2011”. There is a link with the link number “2010” between them.
FIG. 12 shows a link connection diagram in this case. As illustrated in FIG. 12, the control unit 401 of the central device 4 starts and ends events corresponding to the links 2009 to 2011 as interpolation events that are newly added to the node positions of the links 2009 to 2011 in the central device 4. (See hatched triangles in FIG. 12).

The start event and the end event are events indicating that the probe vehicle 5 has passed the start or end of each link 2009 to 2011.
The control unit 401 of the central device 4 adds the newly set start end event and end event between the uplink events in the data table in the second row of FIG. 11 and as related information of the start end event and end event. The passage time obtained by the time calculation process is described in the column “Measurement point measurement time”.

The data table in the third row in FIG. 11 is after the addition of the start and end events and the description of the passage time.
That is, in this case, after the “direction change” in the first row, the end event of the link 2009, the start event of the link 2010, the end event of the link 2010, and the start event of the link 2011 are added. In “Measurement point measurement time”, the passage time calculated by the time calculation process is described.

  If there is a link j and a link j + 1 that are connected to each other, the positions of the start event of the newly set link j and the end event of the link j + 1 match, so the same transit time is described in these events. .

As described above, according to the central device 4 of this embodiment, the control unit 401 adds the link start and end and the calculated passage time to the probe database DB1 that accumulates the probe information S3. The link travel time calculation process is easy to perform.
For example, in the data table of the third row in FIG. 11, when calculating the link travel time of the link 2010, the “link number” field is sorted by “2010” and the “start / end” is selected from the hit data. What is necessary is just to take the difference of the measurement time data whose “flag” is “2” and the measurement time data whose “start / end flag” is “1”.

[Other variations]
The above-mentioned embodiment is an illustration and does not limit the scope of the present invention. The scope of the present invention is indicated by the scope of claims for patent, and all modifications within the scope equivalent to the structure of the claims for patent are included in the present invention.

For example, in the above embodiment, the types of various events that occur in the probe vehicle 5 (single stop, direction change, and constant distance travel) are included in the probe information S3. If there is a time i corresponding to the event information, the event type may not be included in the probe information S3.
In addition, the means for uplinking the probe information S3 to the infrastructure side is not limited to the optical beacon 6, but may be performed by a cellular phone or other radio wave communication means.

  Furthermore, the present invention is not limited to the case where the central device 4 performs wide area control, and the plurality of traffic signal controllers 1a included in the LAN can perform system control or wide area control in a group unit separate from the control by the central device 4. It can also be applied to the case where

DESCRIPTION OF SYMBOLS 1 Traffic signal device 1a Traffic signal control device 2 In-vehicle device 3 Roadside sensor 4 Central device (probe information processing device)
5 Probe vehicle 6 Optical beacon 401 Control unit (determination means, calculation means, data addition means)
403 Communication unit 404 Storage unit DB1 Probe database DB2 Roadside database DB3 Map database

Claims (5)

A probe information processing apparatus that performs processing for obtaining a passage time at the start and end of a link using the position and time of the vehicle included in the probe information,
Determination means for determining whether or not the two points are on the same link based on the positions and times of the two previous points included in the probe information;
When the two points are not on the same link, the time between the two points is used based on the estimated travel time of the link estimated from the roadside measurement information, and the time difference between the two points is used. Calculating means for calculating a passage time at the start and end of the link;
A probe information processing apparatus comprising: The determination means determines whether one or both of the two points coincides with the start and end of the link,
The calculation means calculates the partial travel time by dividing the estimated travel time of the link divided internally by the point by the internal ratio of the link when the determination result is inconsistent, and the partial travel time The probe information processing apparatus according to claim 1, wherein a passage time difference between the two points is allocated based on the point.   The calculation means is based on a distance ratio between the link having the estimated travel time and the link not having the estimated travel time when some of the links between the two points do not have the estimated travel time. The probe information processing apparatus according to claim 1 or 2, wherein distribution of the passage time difference between the two points is performed, and distribution is performed based on a time ratio between the links having the estimated travel time.   The data addition means which adds the start end of the said link and the said passage time after calculation corresponding to this to the database for probes which accumulate | stores the said probe information is further provided. 4. The probe information processing apparatus according to 1. A computer program for causing a computer to execute a process for obtaining a passage time at the start and end of a link using the position and time of a vehicle included in probe information,
Determining whether the two points are the same link based on the positions and times of the two previous points included in the probe information;
When the two points are not on the same link, the start and end points of the link between the two points are allocated by allocating a difference in the passing time between the two points based on the link travel time estimated from roadside measurement information. Calculating the transit time of
A computer program comprising:

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