Contact Traffic Data Collection means that a front-end Data Collection device is placed directly on or under the road surface in contact with the vehicle. Common ground-sensing coil and piezoelectric sensors.

1. Traffic Data Collection-piezoelectric sensor

The principle of the piezoelectric sensor is based on the piezoelectric effect of some dielectrics, which generates a charge on the surface of dielectrics under the action of external force. Therefore, the number and weight of the axles of the passing vehicle can be determined by measuring the extrusion of the piezoelectric sensor equipment.

1) when installed, the damage to the pavement is less, and the same as the buried contact induction equipment, its requirements for the ground incision is only a few square centimeters.

2) provide the accurate number of axles.

3) the equipment is stable in operation and is not easily disturbed by the weather or the change of external magnetic field.

2. Traffic Data Collection-earth-sensing coil sensor

The earth-sensing coil sensor is also called a loop-shaped coil sensor. It is a hollow coil made of several metal wires, which is buried under the road surface of the vehicle and connected with the roadside signal detector and controller, by detecting the induction current in the loop when the vehicle passes through the loop coil, the purpose of detecting the vehicle flow is achieved.

The earth-sensing coil technology is the world's first automation for detecting traffic flow, with 90 percent of all traffic-collection equipment installed in the United States being loop coils.

With time, to adapt to the new needs of the cross-tuning industry, the earth-sensing coil sensor has been suddenly incorporated into more new theories and techniques. At present, in addition to the well-known loop coil sensor (hereinafter referred to as the earth-sensing coil), a small shape and high technical content of magnetic induction coil have been developed and put into the market.

(1) large coil sensor

1) the technology is mature and the cost is low.

2) depending on the induction current generated in the detection coil to judge whether there is a vehicle through, the flow monitoring accuracy is high.

3) vehicle type and speed can be detected (both single-coil and double-coil can be used to distinguish vehicle type, but double-coil can provide relatively high precision vehicle type recognition rate and speed detection rate).

(2) magnetic induction small coil sensor

1) less damage to the road surface when installed, its requirements for the ground incision is not more than 8 cm square circle.

2) because of the use of signal amplifiers and other equipment the front-end of the small coil can be buried 20 cm below the road surface and still maintain a high detection and sensing capacity, while the main control equipment can be placed in the front-end signal acquisition equipment more than a few hundred meters away from the distance, which greatly enhances the convenience and safety of equipment installation.

3) because of the use of the analog signal to digital signal control means, the vehicle recognition rate and speed detection accuracy have been greatly improved.

4) accurate recognition rate of traffic flow.

5) the small coil is made with full-enclosed filling technology, which greatly improves its service life. It is proved by practice that the small coil under the deep-buried road surface can be taken out and used repeatedly.

Due to the different technology, generation, and environment of Traffic Data Collection applications, there are advantages and disadvantages in application and performance. This determines that we need to choose the most suitable Traffic Data Collection according to the specific road conditions and the external environment when we choose the Traffic Data Collection, which has reached the optimization of on-site equipment configuration.