JP4970818B2 - Traffic information creation device, method and program therefor - Google Patents

Description

The present invention relates to a device for acquiring probe data from a probe vehicle equipped with a specific vehicle-mounted device capable of transmitting probe data necessary for collecting traffic information, and creating a traffic information, method and program therefor It is.
Here, the “probe vehicle” refers to a vehicle equipped with a specific in-vehicle device capable of transmitting probe data necessary for collecting traffic information.

  “Probe data” refers to data such as vehicle position, vehicle speed, and passage time acquired by the in-vehicle device. The probe data is data such as vehicle position, speed, passage time, etc., every predetermined time, every predetermined mileage, every predetermined acceleration / deceleration, or every predetermined azimuth change. Contains time data.

Probe data is used to obtain travel time at an arbitrary time. Here, “travel time” means the time required for the vehicle to travel in a predetermined section, and “section” is a target of travel time measurement between expressway interchanges, road links, VICS links, etc. Refers to a section.
Travel time must be a value that assumes a typical vehicle as an indicator of traffic conditions. To calculate traffic information such as travel time using probe data, use a certain number of probe data. Statistical processing needs to be performed.

For example, when calculating travel time, it is reported that if five sets of probe data are obtained, the error from the average value of the traffic situation of the entire passing vehicle including the general vehicle can be reduced to about 5%. As described above, it can be said that it is preferable to collect a certain number or more of probe data and use the average value thereof in order to reduce the error, as in the conventional measurement method.
In a traffic management system that uses probe data that can be collected at a certain collection period, a certain number of probe data may not be obtained at a certain collection period. Even if a calculation process such as travel time is performed based on such a small number of probe data, the accuracy does not increase.

This is because a certain number of probe data cannot be obtained because the ratio of probe vehicles to all vehicles is low.
Generally speaking, as the collection period is set shorter, the travel time can be measured with less delay from the real time, but the number of probe data may not be collected. In addition, the longer the collection cycle is set, the more the probe data is collected. Therefore, the accuracy is improved, but the measurement delay from the real time is increased.
JP 2005-276209 A JP-A-8-106593

  It is an object of the present invention to provide a traffic information generating apparatus, method and program for dynamically changing the collection period of probe data in order to improve information accuracy in calculating traffic information using such probe data. And

The traffic information creation device of the present invention includes an acquisition means for acquiring probe data from a probe vehicle equipped with a specific in-vehicle device capable of transmitting probe data necessary for traffic information collection, and a probe occupying a general vehicle. Calculation means for calculating an optimum collection period for acquiring probe data from a predetermined number or more of probe vehicles based on at least one of the vehicle presence ratio and the number of probe vehicles passing through and the traffic volume on the road And creation means for creating traffic information based on the probe data acquired within the collection period.

  According to the present invention, since the optimum collection period is calculated for acquiring the probe data, it is surely necessary while minimizing the measurement delay with respect to the real time even when the ratio of the probe vehicle and the traffic volume are small. A large number of probe data can be collected. Therefore, the calculation accuracy of traffic information does not decrease, and the device can always be effective for maintaining and stabilizing the accuracy of traffic information.

The calculation unit can show the content of the probe vehicles occupying the general vehicle, at least one of the number passing the probe vehicle, on the basis of the traffic volume of the road, you calculate the collection period. The ratio of the number of probe vehicles to general vehicles, that is, the value obtained by dividing the number of probe vehicles passing by the traffic volume of the road is large, and the more traffic on the road, the shorter the collection cycle and the real-time nature of traffic information Can do. Further, when the proportion of probe vehicles in the general vehicle is small and the traffic volume on the road is small, the collection cycle can be lengthened to maintain the calculation accuracy of traffic information.

The traffic information creation method and program according to the present invention are a method and program according to the substantially same invention as the traffic information creation apparatus.

  As described above, according to the present invention, since the optimum collection period is calculated for obtaining probe data, even when the proportion of probe vehicles and the traffic volume are small, the measurement delay with respect to real time is minimized. Certainly, the necessary number of probe data can be collected. Therefore, the calculation accuracy of traffic information does not decrease, and the device can always be effective for maintaining and stabilizing the accuracy of traffic information.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a block diagram showing the overall configuration of a traffic information creation apparatus according to the present invention.
The traffic information creation device includes a ground traffic center 3 and vehicle detectors 1 and 2. The vehicle detectors 1 and 2 are vehicle detectors such as an ultrasonic type, a loop coil type, and an optical type, and measure the traffic volume (the number of passing units per unit time) on which traffic information is to be created.

The ground traffic center 3 includes a processing device 31 and a road device 5 for communicating with the in-vehicle device.
As shown in FIG. 1, the processing device 31 is installed in the same place as the road device 5, but is not necessarily installed in the same place, and is installed in a location different from the road device 5. It may be connected by a communication line.

The in-vehicle device 6 is mounted on the probe vehicle. Each on-vehicle device 6 has a code for vehicle identification, and can communicate with the on-road device 5 using this code.
The in-vehicle device 6 of the probe vehicle includes a position detection device such as a GPS receiver together with the communication device, and can detect the position of the host vehicle for each time.
Position data, speed data, and the like acquired by the in-vehicle device 6 of the probe vehicle are transmitted from the in-vehicle communication device as probe data. The transmitted data is received by the road device 5 and sent to the processing device 31.

As a method of road-to-vehicle communication between the in-vehicle device 6 and the on-road device 5, a bidirectional communication method such as an optical beacon, wireless LAN, or DSRC (Dedicated Short Range Communication) can be used. Further, communication that directly connects the vehicle and the ground transportation center 3 may be used by a mobile phone, a dedicated radio, or the like.
FIG. 2 shows a format of probe data transmitted from the in-vehicle device 6 of the probe vehicle.

The probe data is composed of items such as the time when the probe vehicle acquired data, the latitude, longitude, altitude, speed, direction of the probe vehicle, and other items (vehicle equipment information, positioning information, DOP [Dilution of Precision], etc.). The
In order to reduce the amount of data, information at the first time (starting edge information) is recorded, and in the data storage part, the time difference, latitude difference, longitude difference, speed difference, azimuth difference, time difference, etc. The difference information from the value of is stored.

The probe data of the probe vehicle is received by the road device 5 and accumulated in the ground traffic center 3.
Here, the collection period of probe data in the ground traffic center 3 is T (minutes).
The probability that probe data can be obtained from n or more probe vehicles in one collection period is written as s (n). s (n) is obtained as follows.

It is assumed that p vehicles pass through the road device 5 in one collection period. Among these, the probability that n probe vehicles pass is
pCn (k) ⁿ (1-k) ^pn
It is represented by k is a ratio in which probe vehicles exist in all vehicles.
The probability s (n) that n or more probe vehicles pass is
s (n) = 1-ΣpCi (k) ⁱ (1-k) ^pi
(Total Σ is taken from i = 0 to i = n−1).

Therefore, s (n) can be obtained if the ratio k in which the probe vehicles are present in all the vehicles and the passing number p per collection period are determined.
On the other hand, there are (60 / T) collection periods per hour. Therefore, the probability that probe data is obtained from n or more probe vehicles in all cycles over one hour is s (n) ^{(60 / T)} .

If probe data was obtained only from less than n probe vehicles in one collection period, this period was said to be “missing”.
Since the collection cycle is obtained (60 / T) times per hour, the probability of “missing” once among the (60 / T) collection cycles is
{(60 / T) -1} / (60 / T)
It is.

The probability s (n) (60 / T) that probe data can be obtained from n or more probe vehicles in all cycles is higher than the probability of “missing” once in (60 / T) collection cycles. The collection cycle T may be selected so that That is,
s (n) ^{(60 / T)} > {(60 / T) -1} / (60 / T) (1)
It becomes.

The meaning of the above formula (1) is as follows. Assume that it is necessary to use n or more probe data per collection period in order to obtain a travel time value at an arbitrary time. It is preferable to obtain T satisfying the above expression (1) as the time T of one collection period necessary for reliably obtaining n pieces of probe data.
Since s (n) in the equation (1) changes depending on the traffic volume and the existence ratio of the probe vehicle, the collection period T necessary for reliably obtaining a certain number of probe data is also the traffic volume and the probe vehicle. Of course, it is influenced by the size of the ratio.

For example, in an operation system using five or more probe data per collection cycle, a theoretical value for the collection cycle T for obtaining five or more probe data on a two-lane road is calculated. become that way.
In FIG. 3, the collection period T is calculated for the case where the number of passing vehicles per hour per lane is 600, 900, 1200, 1500, 1800, 2400.

The graph of FIG. 3 shows that the collection period T can be shortened as the proportion of probe vehicles is increased. Further, it is shown that the collection period T is shorter as the number of passing vehicles is larger.
For example, if the proportion of probe vehicles is 5%, on routes with a traffic volume of 1500 [vehicles / hour / lane] or more, if the collection period T is about 5 minutes, 5 or more probe data will be used. Measured values can be obtained, and if the ratio of probe vehicles is about 15%, if the collection cycle T is about 4 minutes, the route has a traffic volume of 600 [vehicles / hour / lane] or more. It has been shown that measurement values can be obtained using data of five or more probes.

Based on the above considerations, the traffic situation and the ratio of probe vehicles are estimated from the ETC identification information and the tracan data, the optimum collection period shown in the graph of FIG. 3 is obtained, and the collection period T in accordance with these estimation results. If it is dynamically changed, it will be possible to provide stable travel time information with small errors.
FIG. 4 is a flowchart performed by the processing device 31 for each travel time measurement target section, taking travel time calculation as an example.

All or part of the processing described below is realized by the computer of the processing device 31 executing a program recorded on a predetermined medium such as a CD-ROM or a hard disk.
The processing is performed every processing cycle D minutes. First, a processing cycle is started (step S1). Here, the processing cycle D is a cycle for determining the collection cycle T, and within the processing cycle D, the determined fixed collection cycle T is used. In general, D <T when the presence ratio of the probe vehicle is small or the traffic volume is small.

Next, the traffic situation is grasped (step S2). Specifically, the traffic volume is obtained by the vehicle sensor in the section, and the probe vehicle ratio is determined by dividing the number of probe vehicles that have transmitted the probe data to the road device in the section by the traffic volume. .
Next, on the basis of the equation (1), a collection period T at which probe data for n probe vehicles is reliably obtained is determined (step S3). The determined collection period T may be the same as or different from the collection period determined in the past. When the traffic volume decreases with time, the collection period T tends to increase. When the traffic volume increases with time, the collection period T tends to decrease.

The probe vehicle is awaited using this collection cycle T (step S4).
When the current processing period D is completed (step S5), smoothing calculation using the smoothing weight (step S14) is performed on the travel time data based on the collection period T.
If the current processing period D has not ended, it is determined whether new probe data has been acquired (step S6). If acquired, travel time analysis for the section is performed based on the probe data (step S6). S7).

  If there is no speed fluctuation (abnormal driving behavior) exceeding the threshold value (step S8) and the speed is not faster than the threshold value (step S9), such as large variations in speed, the travel time data reliability of the probe vehicle is high. Then, a smoothing weight γ is given (step S12). If the speed is faster than the threshold value, the smoothing weight β is assigned assuming that the travel time data of the probe vehicle has low reliability (step S11). If there is a speed fluctuation (abnormal driving behavior) that is equal to or greater than the threshold value, the smoothing weight α is assigned assuming that the travel time data of the probe vehicle has the lowest reliability (step S10). There is a relationship of α <β <γ.

These travel time data are stored in the memory together with the smoothing weight (step S13).
As described above, the collection period T at which probe data of n probe vehicles can be reliably obtained is dynamically determined, and the probe vehicle is awaited using this collection period T, thereby maintaining the calculation accuracy of travel time. can do.

  Although the embodiments of the present invention have been described above, the embodiments of the present invention are not limited to the above-described embodiments. For example, as the traffic information to be created, detection of sudden events other than travel time can be cited.

It is a block diagram which shows the whole structure of the preparation apparatus of the traffic information of this invention. It is a figure which shows the item example of the probe data transmitted from the vehicle-mounted apparatus 6 of a probe vehicle. It is the graph which calculated the theoretical value for the collection period T for obtaining the probe data more than the predetermined number per collection period. It is a flowchart for demonstrating the example of a measurement of the travel time which the processing apparatus 31 performs.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 2 Vehicle detector 3 Ground traffic center 5 Roadside apparatus 6 Car-mounted apparatus 31 Processing apparatus

Claims (3)

An acquisition means for acquiring probe data from a probe vehicle equipped with a specific in-vehicle device capable of transmitting probe data necessary for traffic information collection;
Calculation for calculating an optimal collection period for acquiring probe data from the probe vehicle based on at least one of the proportion of probe vehicles in the general vehicle and the number of probe vehicles passing through and the traffic volume on the road Means,
A traffic information creating apparatus comprising: creating means for creating traffic information based on probe data acquired within the collection period. The proportion of probe vehicles occupying the collection period required for general vehicles in order to obtain the probe data from the probe vehicle equipped with a specific vehicle device capable of transmitting the probe data required for traffic information collection And based on at least one of the passing number of probe vehicles and the traffic volume of the road ,
Obtain probe data within the collection period from the probe vehicle,
A traffic information creation method, wherein traffic information is created based on probe data acquired within the collection period. A program executed by a computer processing unit for creating traffic information to obtain the probe data from the probe vehicle equipped with a specific vehicle device capable of transmitting the probe data required for traffic information collection And
A procedure for calculating a collection period necessary for acquiring the probe data based on at least one of the ratio of probe vehicles existing in general vehicles and the number of probe vehicles passing through and the traffic volume on the road ;
A procedure for acquiring probe data within the collection period from a probe vehicle;
And a procedure for creating traffic information based on probe data acquired within the collection period.

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