JP3375968B2 - Magnetometer vehicle detector - Google Patents

Description

Description: BACKGROUND OF THE INVENTION The present invention relates to road vehicle detectors, and more particularly to magnetometer detectors for detecting vehicles on the road.

The traffic vehicle detector of the present invention comprises a wire loop that functions as an electric inductor together with a capacitor in an oscillation circuit that detects the presence or absence of a vehicle such as a passenger car, a truck, or a bus. In such a detection system, it is necessary to insert wire loops into the eight notches provided on the pavement surface and install the wire loops below the pavement surface.
A rectangular loop about 4 feet on a side is needed to be sensitive enough to detect small vehicles.

The wire loop itself suffers from a high failure rate. The causes of failure are pavement ridges and differences in the rate of expansion of the pavement material and the wire. When the temperature rises or falls extremely, the wire breaks. In the event of a wire loop failure, it is necessary to install the replacement loop at a location off the failed first loop. Replacing the loop in place is very difficult, so
Place the replacement loop in the off position as described above. However, if the replacement loop is provided at a position outside the optimum position, the arrangement is not optimal, and as a result, the accuracy and accuracy of vehicle detection deteriorate.

A traffic technician who collects information using wire loops needs not only information about the presence or absence of vehicles, but also information such as the number of vehicles, speed, inter-vehicle distance or heading, occupancy, and vehicle type. There is. Although the number of vehicles can be known in a wire loop, it is not possible to know the speed of a vehicle in a single loop because the speed depends on the time required for the vehicle to pass between two points. Even with two loops, it is not possible to obtain sufficient temporal resolution to know the accurate speed of the passing vehicle. Inter-vehicle distance is the distance between vehicles in the same lane, and current wire loops lack sufficient space resolution to accurately measure inter-vehicle distance, especially the distance between vehicles that are close to each other. Occupancy is a measure of whether or not a running or stopped vehicle is in the lane. Current wire loop detectors lack the ability to accurately detect vehicles below a certain speed and therefore cannot always detect stationary vehicles. Also,
In the wire loop, it is not possible to obtain information about the type of vehicle passing through the loop. This is because the measuring coil cannot reveal the characteristics of the vehicle, especially when the SN ratio of the detection signal is relatively low.

SUMMARY OF THE INVENTION In the present invention, it is necessary to place one or more magnetometers, especially magnetoresistive detectors, in each lane of a road or highway. The detector may be placed in a standard scoring groove in a highway or may be inserted in a pipe installed across a subpaved roadbed. Magnetoresistive transducers are advantageous when compared to other magnetometers. The magnetoresistive sensor is a small permalloy magnetometer that can be made to fit within a standard width pave cut. Multiple permalloy magnetometers can be connected with a single cable and placed at predetermined intervals to measure certain vehicle parameters. Permalloy magnetoresistive sensors are solid state sensors and can be manufactured at low cost. Unlike prior art flux gate magnetometers, the current magnetoresistive sensor trussducer support electronics is housed within the magnetometer unit. As you add multiple loops to the same cable in your facility, the sensitivity of wire loops decreases.

Compared to wire loops, magnetometers have a number of advantages and features. Magnetometers are effective for bridge decks that include steel and those that do not have loop cuts in the deck pavement. With fragile pavement,
Magnetometers have a longer life than ordinary wires. Magnetometers require few cuts in the pavement to be installed on the road, and the straight length of the cut is very short. Magnetometers are more sensitive than wire loop sensors (ie, magnetometers can also detect bicycles). This high sensitivity results in a high signal-to-noise ratio, and thus more accurate data can be collected. According to the magnetometer, only 2 feet apart
Each vehicle can be detected separately. In addition, the magnetometer can accurately detect even a vehicle that is not running. When the magnetometer is buried shallowly, the vehicle can be identified by vehicle type and model from various magnetic magnetometer patterns that appear as the main components of the signal when the vehicle passes through the magnetometer.

[Brief Description of Drawings] FIG. 1 is a view showing a normal state in which a wire loop detector according to the prior art is installed on a road.

  FIG. 2 is a diagram showing the road equipment of the present invention.

FIG. 3 is a diagram showing a state in which a magnetoresistive sensor is installed on a road.

FIGS. 4a to 4c are views showing a state in which a magnetoresistive sensor used on a road is put in a package.

FIG. 5 is a view showing a buried state of a pipe used to arrange a magnetoresistive sensor on a road.

FIG. 6 is a diagram showing an arrangement state of a plurality of magnetoresistive sensors.

FIG. 7 shows that when the vehicle passes over the sensor,
This is the signal generated from the axial magnetometer.

FIG. 8 is an example of a vehicle magnetometer signature generated from a single axis magnetoresistive sensor arranged in a straight line.

Figures 9a to 9e are typical magnetometer patterns for trucks.

10a to 10l are typical magnetometer patterns of various vehicles.

FIG. 11 is a block diagram of the magnetometer sensor control device.

FIG. 12 is a signal processing block diagram of the microcomputer of the control device.

  FIG. 13 is a circuit diagram of a closed loop magnetoresistive sensor.

  FIG. 14 is a circuit diagram of an open loop magnetoresistive sensor.

DESCRIPTION OF PREFERRED EMBODIMENTS FIG. 1 is a diagram showing a typical example in which a loop detector 14 is installed on a road 12. To embed the wire coil of sensor 14, loop 14 requires at least four pave cuts 4 feet long and four corner pave cuts approximately 1 foot long. Also, a long pavement cut 16 from the edge of the road 12 to the loop 14 is required. In an inter-lane group, pavement cuts may cross one or more other lanes of road 12.

FIG. 2 shows a state where one structure of the present invention 10 is installed on the road 12. Magnetoresistive (MR) sensor for each lane
10 are installed. For each lane 21, 22, and 23,
The MR sensor 10 is connected to the edge of the road via a notch slot 16 with connecting wires that reach the handhole 18. Wiring from the sensor can be routed from the handhole 18 to a controller / emulator standard model 170, ie '38
Extends to Controller 20, which is a 6Dell computer supplemental system. The wiring extends from system 20 to the traffic control center.

FIG. 3 is an enlarged view of the MR sensor 10 embedded in the road 12. Standard diamond notch slot 16 on road 12
Is about 3/4 to 1 inch deep and 3/8 inch wide. It is large enough to insert an MR detector 10 that is approximately 1/4 inch wide, 5/16 inch deep, and 2 inches long. Slot the detector 10 and its corresponding connecting lead 24
After insertion into slot 16, slot 16 is filled with epoxy resin filler or other suitable material. Especially when using the open loop magnetometer 80 of FIG. 14, the sensor 10 is physically very small. If the single-axis sensor 10 is vertically arranged so as to block the maximum element of the earth's magnetic field, a good vehicle signal is obtained. The length of the cable 24 is not important. Sensor
The 10 can withstand extreme temperatures, water, various chemicals, and any weather conditions.

4a to 4c are views showing a package type MR sensor 10. As shown in FIG. The sensor 10 package is such that the sensor fits only in the vertical position, with the most sensitive axis
It is designed so as to be arranged in the direction of the detection target vehicle within the standard cutout portion 16 of the road 12 in which the 10 is embedded. Figure 4a shows
An in-line type MR sensor 10 is shown, and FIG. 4b shows an end unit type MR sensor 10. FIG. 4c is a diagram showing the structure of the contents of the MR sensor 10. Inside the sensor 10 of FIG. 4c,
Permalloy magnetic sensor 26 and integrated circuit 28 are shown.

Only one permalloy transducer 26 is shown in FIG.
An electronic device 26 for signal conditioning and data communication is mounted on. Substrate 29 is connected to cable 24 and is sealed with epoxy, neoprene, polyurethane, or other suitable filler. Cable consisting of multiple wires
24 is a power line and a signal line of the sensor 10. The sensor 10 attached to the cable is sized to fit in a standard slot 3/8 inches wide, as shown in FIG. For each lane 21, 22, and 23, three of the sensors 10 are arranged along the same cable 24 and share a common power line. The sensors 10 are spaced a few feet from each other and are adapted to generate the time delayed signals required to measure vehicle length and speed.

In another facility shown in FIG. 5, a standard schedule 40 or a custom-made extruded polyvinyl chloride pipe 30 is installed so as to cross the road 12. In order to horizontally support and hold the detector boats 31, 32, and 33 with respect to the horizontal plane of the road 12, inside the pipe 30, there are opposed guide slots 36 across a diameter. In some cases, the extruded polyvinyl chloride (plastic) pipe 30 is installed in advance when paving an expressway and the sensor 10 is installed later. Existing road
In 12, cut a wide slot and drop a tube or tube into slot 16 to get epoxy resin, concrete,
Or it may be covered with other fillers. The advantage of this type of installation is that the MR sensor 10 can be taken out of the pipe 30 at the edge of the road 12 for maintenance or more MR sensors 10 can be added. Sensor 10 is a lane boat 31,3
Mounted on lanes 2 and 33, the lane boats are located below lanes 21, 22, and 23, respectively. Lane Boat 1/16
Boats 31, 32, and 33 of detector 10 are moved in and out of tube 30 with an inch stainless steel cable connection. Boat 3
1, 32, and 33 slide into tube 30 along guide slot 36. A detector lead 24 for signal and power transmission is connected to each sensor 10. When laying the tube 30 on the concrete roadbed of the road 12, it is tied to the reinforcement bar 40 with nylon ties 38 to prevent the tube 30 from rising when the road 12 is filled with concrete or other material. Sometimes.

FIG. 6 is a diagram showing a sensor arrangement for the road 12 in which there are a plurality of sensors 10 for each of the lanes 21, 22, and 23 of the road 12. At most two slots 16 and 42 are required in each lane. The slot 16 serves as a path for the sensor lead wire 24 from the handhole 18 to the slot 42. Slot 42
Is aligned in parallel with each lane 21, 22 and 23 3
It houses one sensor 10. Each lane has three sensors. By the way, there may be a case where the plural sensors 10 for each lane incorporate two or four or plural MR sensors 10 instead. Multiple sensors in each lane can provide various traffic information such as vehicle length, speed, and headway distance. The sensing axis of the sensor 10 is oriented vertically or at right angles to the surface of the road 12. The sensors in slot 42 are spaced a certain distance from each other (e.g. 1 to 5 yards) so that they can generate sufficient time delay signals to measure vehicle length and speed. . At about the same time the vehicle passes over each MR sensor, the sensors produce a "shadow" of the signal. All sensors 10 in slot 42 in either lane 21, 22, and 23 connect to data station 20 through sensor lead 24 along slot 16 and handhole 18 connected to data station 20 In this state, the signal processor uses the threshold level to distinguish between vehicles in the lane of the sensor 10 to be monitored and vehicles in other lanes, and a "false alarm" is issued. The possibility that it will be done is suppressed as much as possible.

FIG. 7 is a diagram showing three magnetic force components Bx, By, and Bz of a truck passing through a three-axis magnetometer 10 at a distance of 50 feet or more from a road 12, each of which has a number 86, respectively. 87 and 88 are attached. Magnetometer pattern
86, 87, and 88 are similar in shape, but have a larger amplitude when the magnetometer is placed in the subgrade 12. Sensor
For those applications where 10 magnitude and cost are high priorities, using only the z-axis signal 88 (Bz) gives complete information that reveals the number of vehicles, speed, headway, occupancy, and vehicle type. To be

FIG. 8 is a diagram showing an example of a vehicle magnetometer pattern obtained from a linearly arranged single-axis MR sensor in a slot 42 of a lane. Since the distance between the sensors 10 is known, the time T ₁ can be used to know the speed of the vehicle passing through the sensor 10. Repeat the measurement of the time T ₄ between the “shadows” 46 and 48 to check the vehicle speed and increase accuracy. The time difference between shadows 46 and 48 is shadow 44
And the time difference between 46 and 46 is almost the same.

The time T ₂ in FIG. 8 is used to determine the inter-vehicle distance. Since there are multiple signals, you can check the distance between vehicles. Changes in the number of vehicles and the road occupancy of the vehicles over time are graphed using the real-time clock 91 in the system controller 20 of FIG. The computer 20 accumulates data for a period of time, which is charted in the form of "demographic" data and transferred to the remote station 92 via a telephone / modem connection at the convenience of the computer operator.

The width of each signal shadow 44, 46, 48, 54, 56, and 58 is directly related to the size or length of the vehicle. Obviously, the size or length of the vehicle represented by shadows 44, 46, and 48 is less than the size or length of the vehicle represented by shadows 54, 56, and 58. The shadow itself produces a characteristic magnetometer pattern according to the sensitivity, the amount of ferrous metal present in the vehicle, and the proximity of the sensor 10, as the main components, such as the passing vehicle's engine, transmission, axles, etc. Shows the difference. For example, shadows 54, 56, and 58 include a recessed portion that indicates the distance between the two axles of a large vehicle passing over each sensor 10.
There are 52. Some magnetometers can be used to distinguish between different types of trucks and other vehicles. T ₃ is a signal time that represents the length of the vehicle. In order to collect more detailed information, the MR sensor 10
It functions as a "point" sensor that produces a signal based on the magnetic field characteristics in the local region above.

Applying the algorithm of the microcomputer 90,
Variations in the detected magnetometer pattern due to different detector positions and different types of equipment can be considered. For example, the magnetometer pattern for vehicles traveling north-south is different than the magnetometer pattern for vehicles traveling east-west. The software accounts for this difference, so there is no need to reconfigure the system for each sensor 10. Usually the vehicle signal is at a much higher level than the electrical noise of the sensor. As shown in Figures 9a to 9e and 10a to 10l, the coupling of the vehicle magnetometer pattern to the next lane sensor is very small, so mutual coupling between lanes is not a problem. .

Sensor is a 5-ton truck that moves at 30 mph
The signals generated by sensor 10 as it passes over or approaches sensor 10 are shown in FIGS. 9a-9e.
The left side is the front of the truck and the right side is the rear of the truck. The curve 93 in FIG. 9a shows the center of the track passing over the sensor 10. Curve 93 is a clear magnetometer pattern for the front axle, engine, and subsequent undercarriage. Curve 94 in Figure 9b is associated with the sensor 10 between the center of the truck and the tire track. No signal appears on curve 94 before or after the track. Curve 95 in Figure 9c is
This is a signal when a truck tire passes over the sensor 10. Curve 95 represents the clear magnetometer pattern of the front axle, engine, and tandem axle, in that order. Curve 96 in FIG. 9d relates to the tire track of a truck passing 1.5 feet from sensor 10. Curve 96 shows the approximate lateral position of the truck within the lane. Curve 97 in Figure 9e shows that the outer tire track is the sensor.
It represents a truck passing through sensor 10 at a distance of 3 feet from 10. Curve 97 shows that almost no signal is detected in the lane next to the lane of travel of the truck.

Figures 10a to 10l show typical magnetometer patterns for various vehicles traveling at 30 mph. The left side is the front of each vehicle and the right side is the rear of the vehicle. For each magnetometer pattern, one scale on the vertical axis is shown as 1 gamma equal to 10-5 gauss. Curve 98 in Figure 10a
FIG. 4 shows a Volkswagen magnetometer pattern with a rear engine passing just above the sensor 10. FIG.
Curve 99 in FIG. 10b is the magnetometer pattern generated by the sensor 10 in the lane adjacent to the lane of the Volkswagen. The curve 100 in FIG. 10c shows the magnetometer pattern of a Vega station wagon with a front engine passing just above the sensor 10. Curve 101 in Figure 10d
Is a magnetometer pattern generated from the sensor 10 in the lane adjacent to the traveling lane of the vega. Curve 102 in Figure 10e
Is the magnetometer pattern of a Ford sedan of Ford that passes just above the sensor 10. Curve 102 is the front engine followed by the undercarriage. FIG. 10f shows the magnetometer pattern 103 generated from the sensor 10 in the lane adjacent to the Ford lane. Magnetometer pattern in Figure 10g
104 is for a motorcycle. FIG. 10h shows the magnetometer pattern 105 generated from the sensor 10 in the lane adjacent to the lane of travel of the motorcycle. FIG. 10i shows a magnetometer pattern 106 for an 18-wheel semi-track. The magnetometer pattern shows the front engine followed by two trailer spindle assemblies. Magnetometer pattern 107 in Figure 10j.
Is a magnetometer pattern generated from the sensor 10 in the lane adjacent to the traveling lane of the semi-truck. The magnetometer pattern 108 of Figure 10k is for a route bus with a rear engine and two axles. FIG. 10l is a magnetometer pattern 109 generated from a sensor in the lane adjacent to the driving lane of the bus.

When the vehicle type is determined, the speed, the inter-vehicle distance, and even the acceleration characteristic are clarified by matching the magnetometer pattern generated from the sensor 10 arranged along the lane. When the acceleration characteristics and the terrain (that is, uphill, downhill, etc.) are combined, the load on the detection target vehicle can be known. The detection and analysis of the magnetometer pattern provides various information about the vehicle to be detected.

FIG. 11 is a block diagram of controller 20 and remote control / data station 92. Input is made from the sensor 10 to the multiplexer 110 of the controller 20. A microcomputer that is the target of processing with a time tag
In order to digitize the input signal to 90, the sensor signal is multiplexed through one signal line and sent to the analog / digital converter 111. Real time clock 91
Is the time measurement standard of the computer 90. The processed output from the computer 90 includes the number of vehicles 112, the vehicle type 113, the speed distribution 114, the inter-vehicle distance 115, and the like. Also, measured values of other parameters are processed. Computer 90
Output goes through modem 116 in parallel or serial format to remote control / data station 92
Transferred to. The power supply 117 supplies a voltage to the power bus of the sensor.

FIG. 12 is a diagram showing an operation performed by the microcomputer 90 with respect to the signal of the sensor 10. Signals provided 118
Is digitized and time-tagged. Signal 118 proceeds to processing block 119, which is the eighth block.
Time between signal peaks 44 and 46 (T ₁ ) as shown
To decide. Block 120 averages time T ₁ for multiple sensors 10. Then the ratio, sensor spacing / T ₁
Accordingly, block 121 determines the speed of the vehicle, and then processing block 122 averages the speeds. Supply signal 118
Is also processed by block 123. This block consists of a set of signals 44, 46 and 48 and a signal 5 as shown in FIG.
Measure the time (T ₂ ) between 4, 56, and 58 pairs.
The block 124 determines the inter-vehicle distance by multiplying the vehicle speed or the ratio output from the block 121 and the sensor interval / T ₁ by the T ₂ output from the block 123. The block 125 averages the inter-vehicle distances output from the block 124. Block 126 provides a predetermined signal threshold. Block 1
27 compares the signal supplied from block 118 with the above threshold value to determine the value of T ₃ as shown in FIG.
Block 128 averages the values of T ₃ . The average value of T ₃ is transferred to processing block 129 which determines the vehicle type classification and the number of vehicles for each vehicle type. The block 130 classifies the vehicle types in various ways according to the type of information required. For example, T ₃ is classified as a motorcycle when T ₃ is short, a car when T ₃ has an intermediate length, and a truck when T ₃ is long. The average vehicle speed digital information output from block 122, the average vehicle distance digital information output from block 125, and the vehicle classification digital information output from block 130 are processed by block 131 in parallel or serial format. , To the control center or control / data station 92 for transmission to the modem 116.

FIG. 13 is a schematic diagram of an example of the magnetoresistive sensor 10. A permalloy magnetoresistive sensing bridge 50 detects variations in the magnetic signal or magnetic field of the vehicle near the sensor 50. The reset field coil 60 is not necessary, but the sensing coil 50
Resets the magnetization in the easy axis direction. The direction of magnetization of the sensing bridge 50 changes in the range of 0 to 180 ° with respect to the easy axis direction, so that the output of the sensor 50 is insensitive to thermal drift and offset of the bridge 50 in the case of a wide magnetic field. Becomes The output signal leaving the bridge 50 under the action of the vehicle magnetic signal 62 is amplified by the amplifier 64. amplifier
The signal from 64 is integrated by integrator 66. Sensor 10
Is an open loop system, but the output of integrator 66 is
Feedback is provided via feedback coil 68 and integrating capacitor 70 to the input terminal of electronic integrator 66.
The magnetic feedback from the feedback coil is
Feedback to Bridge 50. This magnetic feedback enables the signal output from the sensing bridge 50 by the closed loop method. The closed loop configuration reduces the cross-axis sensitivity and non-linearity of the sensing bridge 50 output to the magnetic signal 62. The resistor 72 loads the output of the integrator 66 and is a factor in the current / voltage conversion of the coil. The analog output of the integrator 66 goes to an analog / digital (A / D) converter 74. The digital signal output of the converter 74 is transmitted to the data transmitter 76. This oscillator manages the digital data transferred to the system 20 digital data bus. For all of the sensor 10 circuitry, power and timing circuitry 78 conditions the signal provided by the system bus and coils the reset signal.
The time measurement signal is supplied to 60, and the time measurement signal is supplied to the integrator 66, the analog / digital converter 74, and the data oscillator 76.

FIG. 14 is a diagram showing a basic magnetoresistive sensor 80 including a magnetoresistive bridge 50 and a differential amplifier 84. Sensor 50
Is a Permalloy bridge, biased "barber pole" to eliminate the need for external magnetic bias. Power regulator 82 is a sensor
The DC voltage required for 80 is supplied from an AC power bus that connects to a roadside station. Compared to the sensor 10 in FIG. 13,
The sensor 80 is less accurate but more economical. Simplified sensor in the absence of closed-loop operating feedback coil 68 and / or reset coil
10 may be used.

Continuation of the front page (56) Reference JP-A-5-232244 (JP, A) JP-A-57-203199 (JP, A) JP-A-64-41996 (JP, A) German Patent Application Publication 3521655 (DE) , A 1) US Patent 3825889 (US, A) US Patent 3775742 (US, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G08G 1/01 G01C 15/00 G01P 3/66 G06M 7 / 00

Claims (7)

(57) [Claims] 1. A magnetometer vehicle detector for roads having at least one lane with at least one magnetometer sensor in each lane, wherein the magnetometer sensor has a sensitivity axis, the change in the ambient magnetic field caused by a motor vehicle. A magnetoresistive bridge that outputs an electric signal generated by a change in resistance due to the vehicle; an amplifier that is connected to the magnetoresistive bridge and that outputs an amplified electric signal indicating the presence or absence of a vehicle; An integrator that outputs an integrated electric signal indicating the presence or absence of a magnetic field; a feedback coil that is connected to the integrator and that is disposed close to the magnetoresistive bridge and that provides magnetic feedback to the magnetoresistive bridge; It is placed near the resistance bridge and the magnetization axis of the bridge alternates between 0 and 180 degrees with respect to the sensitivity axis. A magnetometer vehicle detector, comprising: a reset coil for switching to a switch; 2. A magnetometer vehicle detector according to claim 1, wherein the magnetometer sensor is fitted in a standard cut groove provided on the road, and the sensitivity axis of the magnetometer sensor is in a direction perpendicular to the common plane of the road. 3. A magnetometer vehicle detector for a road having a first surface and a second surface, the first surface having at least one lane, wherein each lane of the road has at least one sensitivity axis. Two magnetometers are provided, the magnetometer has a sensitivity axis, and a magnetoresistive bridge whose resistance changes due to changes in the ambient magnetic field caused by the presence of an automobile; and a magnetoresistive bridge connected to the magnetoresistive bridge, An amplifier for amplifying a voltage change, an analog / digital converter connected to the amplifier, a signal line connected to the analog / digital converter, and a signal processor connected to the signal line are provided. The magnetometer is installed in a notch provided on the road, and its sensitivity axis is in the direction perpendicular to the common plane of the road. And an amplifier connected to the integrator and located proximate to the magnetoresistive bridge to provide magnetic feedback to the magnetoresistive bridge, and the cross-axis sensitivity of the bridge and A magnetometer vehicle detector having a feedback coil for reducing non-linearity. 4. The magnetometer of claim 3, further comprising a reset coil disposed near the magnetoresistive bridge to switch the magnetization axis of the bridge with respect to the sensitivity axis to reduce thermal drift and offset of the bridge. Vehicle detector. 5. The ends are connected to each other to form a bridge and have first, second, third and fourth nodes,
A first node and a third node are respectively connected to positive and negative voltage sources, and a second node and a fourth node have a magnetoresistive bridge with four magnetoresistors connected to the inverting and non-inverting inputs of the amplifier, An output signal from the amplifier is provided by a direct current supplied to the input of the amplifier based on the resistance change of the four magnetoresistive vehicles by a vehicle having at least one magnetometer mounted on the road and approaching or passing by the magnetometer. A magnetometer vehicle detector for roads, which is indicative of the presence of a motor vehicle, wherein each of said magnetometers is arranged at a distance from each other along the length of the road, and a signal processor approaches or approaches the magnetometer. Receiving a group of output signals having pattern characteristics from a magnetometer caused by a vehicle passing by, converting the signals into the number of vehicles and vehicle speed information; A sessa converts the pattern characteristics into vehicle type information for each of the detected automobiles, the signal processor comprises a multiplexer connected to each of the magnetometers, an analog / digital converter connected to the multiplexer, A first microcomputer connected to the analog / digital converter, the microcomputer connected to the analog / digital converter to determine a first time between peaks of a signal; Means for determining the speed of the vehicle from said first time and a predetermined interval, and means for determining a second time between groups of signals, connected to an analog / digital converter A third means, which is connected to the second means and the third means, and which determines the vehicle speed from the vehicle speed and the second time. A fourth means for determining an interval; and a third signal connected to the analog / digital converter, having a predetermined signal threshold value, comparing the pattern characteristics of the signal with the predetermined threshold value, and determining a third time period. A fifth means for judging, a sixth means connected to the fifth means for dividing the third time into vehicle types, and a seventh means connected to the sixth means for determining the number of automobiles. And a magnetometer vehicle detector. 6. The magnetometer vehicle detector of claim 5 further comprising a modem connected to said second, fourth, sixth and seventh means. 7. The magnetometer vehicle detector of claim 6 wherein the magnetometer is a magnetoresistive detector.