JPH04223694A - Traffic flow measuring unit - Google Patents

Abstract

PURPOSE:To suppress cost increase at the extension of a vehicle detector and to improve the processing speed of a primary processor by converting information data that a vehicle detecting signal is information-processed into a communication signal and transmitting it through an existing telephone line. CONSTITUTION:Plural vehicle detectors 1... to convert information data that a vehicle detecting signal is information-processed into a communication signal to possess frequency different from that of a sound signal and to output it and a primary processor 7 to transmit/receive the communication signal by the above mentioned respective vehicle detectors 1... and to establish a data link with the specified vehicle detector 1 by polling are possessed, the above mentioned respective vehicle detectors 1... and the primary processor are connected to pulse transformers 3...5 able to change an output destination by the frequency respectively and the above mentioned pulse transformers 3...5 are connected by a telephone line 9.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention comprises a plurality of vehicle detectors that output traffic information as information signals, and a system that is connected to these vehicle detectors and grasps road conditions based on the traffic information from each vehicle detector. The present invention relates to a traffic flow measuring device having a primary processing device that enables the following.

0002

[Background Art] Understanding road conditions is necessary for road administrators to implement traffic regulations, etc., and has also become necessary for drivers to drive safely and select driving courses. In particular, on expressways where vehicles travel at high speeds, road conditions are closely related to vehicle safety, so it is desired to understand the road conditions more accurately. Therefore,
Road conditions can now be obtained by processing multiple pieces of traffic information collected from multiple locations within a given section, and this collection and information processing is now performed by traffic flow measuring devices. ing.

Conventionally, as shown in FIG. 9, the above-mentioned traffic flow measuring device includes vehicle detectors 52 arranged at predetermined intervals on the sides of an expressway 51, for example, and these vehicle detectors 52...
and a primary processing device 54 connected via a transmission line 53, and each of the vehicle detectors 52 described above outputs a vehicle detection signal as an information signal when it detects a vehicle. There is. Then, these information signals are transmitted to the primary processing device 54 via the transmission line 53, and are sent to the detection signal interface 5 built in this primary processing device 54.
5..., the signal form suitable for the transmission lines 53... is converted into a signal form suitable for the primary processing device 54, and then the information is processed by the primary processing device 54.

[0004] Accordingly, the conventional traffic flow measuring device processes a plurality of pieces of traffic information obtained by each vehicle detector 52 to determine whether the vehicle is within a predetermined section in which these vehicle detectors 52 are installed. It is now possible to accurately understand the road conditions in the area.

[0005]

[Problems to be Solved by the Invention] However, in the conventional traffic flow measuring device described above, when adding the vehicle detector 52, modifications such as adding the transmission line 53 and the detection signal interface 55 in the primary processing device 54 are required. There is a problem that the cost at the time of expansion tends to be excessive.

Further, the information signal output from the vehicle detector 52 is a vehicle detection signal indicating the presence or absence of a vehicle, and when processing the information form of this vehicle detection signal into an information form such as the average speed of the vehicle. This requires a large amount of processing power. Therefore, the primary processing device 54 to which this vehicle detection signal is input as traffic information has a very large processing amount when processing the information, so it uses a CPU (Central Pr.
As a result, the processing speed is significantly reduced in proportion to the number of traffic information inputs.

[0007] As described above, conventional traffic flow measuring devices enable accurate understanding of road conditions by processing multiple pieces of traffic information. If the number of units 52 is increased, there are problems in that the increase in cost at the time of expansion becomes excessive and the processing speed is significantly reduced. Therefore, an object of the present invention is to provide a traffic flow measurement device that can solve the above problem by transmitting traffic information obtained by processing vehicle detection signals into a predetermined information format via a telephone line. It is said that

[0008]

[Means for Solving the Problems] In order to solve the above-mentioned problems, the traffic flow measuring device of the present invention converts information data obtained by processing a vehicle detection signal output from a vehicle detection sensor into a frequency different from that of an audio signal. A primary processing device that transmits and receives communication signals with each of the vehicle detectors and establishes a data link with a specific vehicle detector by polling. ,
Each of the above vehicle detectors and the primary processing device is connected to one side of a telephone exchange or a telephone set, which is an audio communication means that outputs an audio signal, and a slave station, which is a signal switching means that can switch the output destination depending on the frequency. The slave station pulse transformer and the master station pulse transformer are connected to the other of the pulse transformer and the master station pulse transformer, respectively, and the slave station pulse transformer and the master station pulse transformer are connected by a telephone line.

[0009]

[Operation] According to the above configuration, the communication signal transmitted and received between the primary processing device and the vehicle detector and the audio signal output from the audio communication means have different frequencies, and the signal switching means The output destination can be switched by . Therefore, even when an audio signal and a communication signal are input at the same time, the signal switching means outputs the audio signal to the audio communication means connected to one, and outputs the communication signal to the primary processing device or vehicle connected to the other. This will be output to the detector. Switching between the audio signal and the communication signal by this signal switching means prevents interference even if the information signal and the audio signal are superimposed on the telephone line, so it is possible to prevent interference by using the signal switching means. This will make it possible to install the system using telephone lines.

Furthermore, since the primary processing device establishes a data link with a specific vehicle detector by polling, it is possible to add vehicle detectors without modifying the primary processing device. As a result, the traffic flow measurement device does not require additional telephone lines or modification of the primary processing device when adding vehicle detectors, making it possible to suppress increases in costs when adding vehicle detectors.

Furthermore, since the communication signal transmitted from the vehicle detector to the primary processing device is a result of information processing of the vehicle detection signal, the burden required for information processing on the primary processing device is reduced. As a result, it is possible to improve processing speed.

0012

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. 1 to 8.

The traffic flow measuring device according to this embodiment connects a master station and a plurality of slave stations with a pair of telephone lines, and transmits and receives a communication signal having a frequency higher than the voice band by superimposing it on the voice signal. DOV (Data Over Voice)
) method is adopted. This DOV-based traffic flow measuring device uses a communication cable with a diameter of 0.65 mm, for example, which can extend up to a maximum total distance of about 6 km, as a transmission path. The communication signal is FSK (Frequency S
(high keying) method. In addition, the center frequency of the modulated communication signal is 50KHz ± 10KHz (mark 60K) when transmitted from the slave station to the master station.
Hz, space 40KHz), and the transmission from the master station to the slave station is 100KHz ± 10KHz (mark 1
10KHz, space 90KHz).

[0014] Furthermore, this traffic flow measuring device has a
A half-duplex communication method is adopted in which the transmission speed is set to 0 b/s and the access method is set to establish a data link between the master station and a specific slave station by polling, and the transmission level is 0. ~15 dBm, while the transmission level is set to 0 to -24 dBm. The master station and the slave stations connected via telephone lines are connected in a 1:N ratio, and the master station receives information signals sent from all the slave stations at fixed intervals such as 30 seconds. It is designed to collect signals.

Next, the traffic flow measuring device of this embodiment will be explained in detail. As shown in FIG. 1, the traffic flow measuring device is installed in a telephone network installed on an expressway 4, for example, and includes a primary processing device 7 as a master station and a vehicle detector as a slave station. 1... are connected by a pair of telephone lines 9. This telephone network includes telephones 2, which are voice communication means, and a telephone exchange 6, which are arranged at predetermined intervals, slave station side pulse transformers 3, which are signal switching means, and master station side pulse transformers 5, It consists of a telephone line 9.

As shown in FIG. 3, the parent station side pulse transformer 5 has two parent input/output sections 5a and 3b and one transmission input/output section 5c. The output section 5a and the transmission input/output section 5c are configured to pass only signals having a frequency of 4.7 KHz or less, while the other parent input/output section 5b and transmission input/output section 5c are configured to pass a signal having a frequency of 10 KHz or less.
Only signals with frequencies above this are allowed to pass through.

Further, as shown in FIG. 4, the slave station side pulse transformer 3 has two slave input/output sections 3a and 3b and one transmission input/output section 3c. The output section 3a and the transmission input/output section 3c are configured to pass only signals having a frequency of 4.7 KHz or less, while the other child input/output section 3b and transmission input/output section 3c are configured to pass a signal having a frequency of 10 KHz or less.
Only signals with frequencies above this are allowed to pass through.

A telephone 2 is connected to one of the slave input/output sections 3a, and a signal of 0.3 to 3.4
A signal obtained by converting an audio signal having an audible frequency of KHz into an electrical signal is input. On the other hand, the other secondary input/output section 3b is connected to a vehicle detector 1 that outputs an information signal set at a frequency of 10 KHz or higher, which serves as traffic information, as a communication signal.

The vehicle detector 1 described above, as shown in FIG. As shown in FIG.
It is housed in 3. Further, as shown in FIG. 2, the vehicle detection means 10 includes vehicle detection sensors 10a and 10 of a loop coil type, an ultrasonic type, an acoustic type, or an infrared type.
The vehicle detection sensor 10a is located on the upstream side of the road, while the vehicle detection sensor 10b is located on the upstream side of the road.
It is arranged downstream at a predetermined distance L from the vehicle detection sensor 10a. Then, the above-mentioned both vehicle detection sensor 1
0a and 10b are adapted to output H-level vehicle detection signals D1 and D2 when detecting the presence or absence of a vehicle.

The vehicle detection means 10 described above is connected to a waveform shaping circuit 11 of the main body of the detector.
corrects overshoots and undershoots of vehicle detection signals D1 and D2 input from each vehicle detection sensor 10a and 10b, and also corrects delays in vehicle detection signals D1 and D2 and external noise other than vehicle detection signals D1 and D2. It is designed to be removed. And this waveform shaping circuit 1
1 indicates vehicle detection signals D1 and D2 below a certain voltage level.
information processing means 2 via a level detection circuit 12 that removes
Connected to 1.

The above information processing means 21 includes a vehicle number integration circuit 13, a time difference measurement circuit 14, and a vehicle presence/absence time measurement circuit 15.
, recording circuit 16, speed calculation circuit 17, occupancy rate calculation circuit 1
8, and a transmission circuit 19, the level detection circuit 12 described above includes a number integration circuit 13, and a time difference measurement circuit 1.
4, and a vehicle presence/absence time measuring circuit 15. The above-mentioned vehicle number integration circuit 13 has a predetermined time such as 1 minute, 3 minutes, 5 minutes, etc. as a measurement unit time, and the rise of the vehicle detection signal D1 input to H level per this measurement unit time. It is calculated as the number of vehicles passing through. The number-of-vehicles accumulation circuit 13 is connected to a recording circuit 16 to store the accumulated number of vehicles in a number-of-vehicles recording area formed in the recording circuit 16.

Further, the time difference measuring circuit 14 is connected to the above-mentioned recording circuit 16 via a speed calculating circuit 17.
As shown in FIG. 6, the time difference td between vehicle detection signals D1 and D2 from both vehicle detection sensors 10a and 10b is measured, and as shown in FIG. 1, this time difference td is output to the speed calculation circuit 17. ing. The speed calculation circuit 17 to which the time difference td is inputted is the vehicle detection sensor 10a.
The vehicle speed is calculated by substituting the distance L between 0b and the time difference td into the following calculation formula (1), and the vehicle average speed obtained by averaging each vehicle speed V obtained in the measurement unit time is stored in the recording circuit 16. The speed is stored in the created speed storage area.

[0023]V = 3.6・L/T...(1
) In addition, V is the vehicle speed V [km/h], and L is the distance L [m].
, and T are the time differences td [sec]. Further, the vehicle presence/absence time measuring circuit 15 is connected to the recording circuit 16 via the occupancy rate calculation circuit 18, and one vehicle detection signal D
1 H level time is integrated, and this integrated value is output to the occupancy rate calculation circuit 18 as the vehicle available time. Then, this occupancy rate calculation circuit 18 calculates the occupancy rate by dividing the input vehicle available time by the measurement unit time, and stores this occupancy rate in the occupancy rate recording area formed in the recording circuit 16. ing.

The recording circuit 16 that records the information data consisting of the number of vehicles, average vehicle speed, and occupancy rate is connected to a transmission circuit 19 that converts the information data into a predetermined format suitable for transmission. Information data is output to the transmission circuit 19 when a data link is established by polling. And this transmission circuit 1
9 is connected to a modem 20 which outputs information data as a communication signal that is an FM-modulated information signal and demodulates the input communication signal.

Although the information processing means 21 described above is composed of hardware, it is not limited to this, and may be composed of a microcomputer having software that can execute similar operations. Also good.

As shown in FIG. 1, the vehicle detector 1 having the modem 20 described above is connected to the transmission input/output section 5c of the master station pulse transformer 5 via the slave station pulse transformer 3 and the telephone line 9. ing. This master station side pulse transformer 5
Like the slave station side pulse transformer 3 described above, it has two parent input/output sections 5a and 5b and one transmission input/output section 5c, and one parent input/output section 5a and one transmission input/output section 5c. What is the output section 5c?
The main input/output section 5b and the transmission input/output section 5c are designed to pass only signals having a frequency of 4.7 KHz or lower, while the other parent input/output section 5b and transmission input/output section 5c are designed to pass only signals having a frequency of 10 KHz or higher. It has become.

The master station pulse transformer 5 has one parent input/output section 5a connected to the telephone exchange 6, and receives an audio signal of an audible frequency from the telephone 2 inputted to the slave input/output section 3a. It is designed to selectively output only the information to the telephone exchange 6. Further, the other parent input/output section 5b of the parent station side pulse transformer 5 is connected to the detection signal interface 8 of the primary processing device 7, and receives information signals from the vehicle detector 1 inputted to the slave input/output section 3b. The primary processing device 7 is configured to selectively output only the processed data to the primary processing device 7.

In the above configuration, the operation of the traffic flow measuring device will be explained below.

First, the operation of the vehicle detector 1 will be explained. As shown in FIG.
b is a vehicle detection signal D at H level when a vehicle is detected.
1 and D2 are output to the waveform shaping circuit 11. These vehicle detection signals D1 and D2 are waveform-shaped by removing external noise, overshoot, and undershoot in a waveform shaping circuit 11, and then information processing is performed in a level detection circuit 12 only for signals above a predetermined voltage level. It will be output to means 21.

At this time, when the information processing means 21 is constituted by hardware, the vehicle detection signal inputted to the information processing means 21 is transmitted to the vehicle number integration circuit 13, the time difference measurement circuit 14, and the vehicle presence/absence time measurement circuit. 15, and in the vehicle number integration circuit 13, the H of the vehicle detection signal D1
A rise to the level is recognized as a new vehicle, and the number of times this rise is added up. Then, the integration in the number-of-units integration circuit 13 is continuously executed during the measurement unit time, and the integrated value when the measurement unit time has elapsed is stored as information data in the number-of-units recording area of the recording circuit 16. That will happen.

The vehicle detection signals D1 and D2 inputted to the time difference measuring circuit 14 have a time difference td in rising to the H level, and this time difference td is calculated by the speed calculation circuit 1.
7 will be input. Then, the speed calculation circuit 17
The time difference td input to the vehicle detection sensor 10a.
The distance L between 0b and 0b will be used to calculate the vehicle speed, and the calculated vehicle speed is averaged within the measurement unit time and then stored in the speed storage area of the recording circuit 16 as information data. That will happen.

Further, the vehicle detection signal inputted to the vehicle presence/absence time measuring circuit 15 measures the time when it is at H level, and this time is used as the vehicle presence time by the occupancy rate calculation circuit 18.
will be entered into. Then, the occupancy rate calculation circuit 18
The vehicle occupancy time inputted into the measurement unit time will be used to calculate the occupancy rate, and this occupancy rate will be stored in the occupancy rate recording area of the recording circuit 16 as information data.

On the other hand, when the information processing means 21 is configured by software, the time difference detection processing routine is executed by inputting the vehicle detection signal from the level detection circuit 12.

That is, when the time difference detection processing routine is executed, the time domain is cleared to zero and the timer count is started when the vehicle detection signal rises to the H level, as shown in FIG. S1). and,
After the timer count-up operation of adding 1 to the above time domain is executed (S2), the vehicle detection signal D1 from the vehicle detection sensor 10a is taken in (S3), and whether the vehicle detection signal D1 is at H level or not is determined. (S4).

If it is determined in S4 that the vehicle detection signal D1 is at the L level, then NO is returned to S5.
will be executed, and after the timer count value Tpi, which is the integrated value in the time domain, is stored as the available time of each vehicle (S5), the process will be terminated (S6). on the other hand,
If it is determined that the vehicle detection signal D1 is at the H level, S7 is executed as YES, and the vehicle detection signal D2 from the vehicle detection sensor 10b is taken in (
In S7), it is determined whether the vehicle detection signal D2 is at H level. If it is determined that the vehicle detection signal D2 is at the L level, the answer is NO and S2 is re-executed, whereas if it is determined to be at the H level, the answer is YES and S9 is executed again. (S8).

When S9 is executed, the timer count value Tdi, which is the integrated value in the time domain, is stored as the time difference td (S9). After this, the distance L between the vehicle detection sensors 10a and 10b is determined using the above timer count value Tdi.
The individual vehicle speed Vi is calculated by dividing (S10),
After the number of machines is counted by adding 1 to the counting area (S11), the process is re-executed from S2.

The above-described time difference detection processing routine is repeatedly executed until the measurement unit time has elapsed, and when the measurement unit time has ended, the measurement processing routine is executed.

When the measurement processing routine is executed,
As shown in FIG. 8, the integrated value of the counting area obtained by performing the number-of-units counting is stored as the number-of-units count value n (S21). After this, the individual vehicle speeds Vi calculated in the time difference detection processing routine are added (S22), and this added value (V1+...+Vn) is divided by the number of vehicles count value n to calculate the vehicle average speed Vs (S23). , this vehicle average speed Vs will be stored in the speed storage area (
S24).

Next, in the time difference detection processing routine, the individual timer count values Tpi stored as the vehicle available time are added (S25), and this added value (Tp1+...+Tpn
) is divided by the measurement unit time to calculate the occupancy rate (S2
6), this occupancy rate is stored in the occupancy recording area (S27). Thereafter, the stored data such as the number count value n, vehicle speed Vi, and timer count value Tpi stored in each area are cleared (S28), and the process is ended (S29).

[0040] Information data consisting of the number of vehicles, average vehicle speed, and occupancy rate formed by the information processing using the software and hardware described above is transmitted to the vehicle detector 1 and the primary processing device 7 as shown in FIG. will be output to the modem 20 in FIG. 2 when a data link is established by polling. In addition, 100KHz during the above polling
A communication signal of ±10 KHz will be output to the primary processing device 7. The information data input to this modem 20 is FM-modulated into an information signal of 50 KHz±10 KHz and converted into a communication signal, and then sent to the pulse transformer 3 on the slave station side.
The signal is then transmitted to the master station pulse transformer 5 via the telephone line 9.

By the way, the voice signal from the telephone set 2 is also transmitted to the above-mentioned telephone line 9, and the master station pulse transformer 5 receives the voice signal as well as the communication signal.

At this time, the master station side pulse transformer 5 allows the transmission input/output part 5c and the master input/output part 5b to pass only signals having a frequency of 10 KHz or more, while the transmission input/output part 5c and the master input/output part 5b The section 5a is designed to pass only signals having a frequency of 4.7 KHz or less. Therefore, the communication signal and the audio signal are separated by the master station pulse transformer 5, and the communication signal is output from the master input/output section 5b to the detection signal interface 8 of the primary processing device 7. , the audio signal is output from the main input/output section 5a to the telephone exchange 6.

Furthermore, when transmitting a communication signal such as a control signal from the primary processing device 7 to the vehicle detector 1, since the communication signal is FM modulated at 100 KHz±10 KHz, the voice from the telephone exchange 6 is Even if the signal is superimposed, the communication signal and the audio signal will be separated by the pulse transformer 3 on the slave station side, and the communication signal will be received by the vehicle detector 1 without interference with the audio signal. .

As described above, the traffic flow measurement device of this embodiment is configured to adjust the frequency of the communication signals transmitted and received between the primary processing device 7 and the vehicle detector 1 . The frequency of the audio signal is made different, and the output destinations of the communication signal and the audio signal are switched between the master station pulse transformer 5, the slave station pulse transformer 3, and so on. Therefore, the traffic flow measuring device can be installed using the existing telephone line 9 since there is no interference even when communication signals and voice signals are superimposed on the telephone line 9. . In addition, the primary processing device 7 and the vehicle detector 1...
To establish a data link by polling,
The detection signal interface 8 of the primary processing device 7 is not related to the number of vehicle detectors 1 installed. As a result, the traffic flow measuring device does not require modification by adding telephone lines 9 or detection signal interfaces 8 even if vehicle detectors 1 are added, making it possible to suppress the increase in cost when adding more. It has become.

Furthermore, the communication signal transmitted from the vehicle detector 1 to the primary processing device 7 is an information signal obtained by processing the vehicle detection signals D1 and D2 into the number of vehicles, average vehicle speed, and occupancy rate. The burden on the processing device 7 required for information processing is reduced, and as a result, it becomes possible to improve the processing speed. Furthermore, as shown in FIG. 5, a detector box 23 that accommodates the vehicle detector 1 can be installed on the back of the telephone booth 22. Therefore,
The traffic flow measuring device does not require securing an installation location or installing new installation equipment, and the number of vehicle detectors 1 can be easily increased.

Note that the information signal in this embodiment is information data consisting of the number of vehicles in a single lane, average vehicle speed, and occupancy rate, but is not limited to this, and can be information data of multiple lanes. It's okay to have one. In order to obtain information data for multiple lanes, first, information data for each lane, such as the number of vehicles (n1, n2, ..., nk), average vehicle speed (v1, v2, ..., vk), and occupancy rate (tp1, t
p2,...,tpk) are accumulated. Then, the total number of vehicles N, which is the sum of the number of vehicles (n1, n2, ..., nk) for each measurement unit time, the total average vehicle speed, which is the sum of the average vehicle speeds (V1, V2, ..., Vk), and the occupancy rate. (tp1, tp2,
..., tpk), and the total vehicle average speed and total occupancy rate are divided by the total number of vehicles N to calculate the vehicle average speed and occupancy rate. As a result, the traffic flow measurement device can calculate the number of vehicles in multiple lanes, average vehicle speed,
It becomes possible to transmit and receive information data consisting of information and occupancy rates as information signals.

[0047]

Effects of the Invention As described above, the traffic flow measurement device of the present invention includes a plurality of vehicle detectors that convert information data obtained by information processing of a vehicle detection signal into a communication signal having a frequency different from that of an audio signal and output the communication signal. and a primary processing device that transmits and receives communication signals with each of the vehicle detectors and establishes a data link with a specific vehicle detector by polling, and each of the vehicle detectors and the primary processing device are connected to one another. An audio communication means for outputting an audio signal is connected to the other of the signal switching means capable of switching the output destination depending on the frequency, and each of the signal switching means is connected by a telephone line. .

[0048] As a result, even if a voice signal and a communication signal are superimposed on a telephone line, interference is prevented by the signal switching means, so it is possible to install the traffic flow measuring device using an existing telephone line. In addition, since the primary processing unit establishes a data link with a specific vehicle detector by polling, it becomes possible to add vehicle detectors without modifying the primary processing unit. It becomes possible to suppress the increase in cost when installing additional detectors.

[0049] Furthermore, since the communication signal sent from the vehicle detector to the primary processing device is the one obtained by processing the vehicle detection signal, the burden required for information processing on the primary processing device is reduced, and as a result, This has the effect that processing speed can be improved.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram of a traffic flow measuring device.

FIG. 2 is a block diagram of a vehicle detector.

FIG. 3 is a schematic configuration diagram of a master station pulse transformer.

FIG. 4 is a schematic configuration diagram of a slave station side pulse transformer.

FIG. 5 is a perspective view showing the installed state of the detector box.

FIG. 6 is a waveform diagram of a vehicle detection signal.

FIG. 7 is a flowchart of a time difference detection processing routine.

FIG. 8 is a flowchart of a measurement processing routine.

FIG. 9 is a schematic configuration diagram of a conventional traffic flow measuring device.

[Explanation of symbols]

1 Vehicle detector 2 Telephone (voice communication means) 3 Slave station side pulse transformer (signal switching means) 4 Expressway 5 Master station side pulse transformer (signal switching means) 6 Telephone exchange (voice communication means) 7 Primary processing device 8 Detection signal interface 9 Telephone line 10 Vehicle detection means 10a and 10b Vehicle detection sensor 20 Modem 21 Information processing means 23 Detector box

Claims (1)

[Claims] Claim 1: A plurality of vehicle detectors that convert information data obtained by processing information on a vehicle detection signal into a communication signal having a frequency different from an audio signal and output the same, and each of the vehicle detectors transmits and receives a communication signal. , and a primary processing device that establishes a data link with a specific vehicle detector by polling, and each of the vehicle detectors and the primary processing device are connected to one end of an audio communication means that outputs an audio signal, and a frequency 1. A traffic flow measuring device, wherein the signal switching means is connected to the other one of the signal switching means capable of switching an output destination by a telephone line.