Local Traffic condition detection

How to evaluate traffic status

• Evaluation indicators: flow, speed and density

Traffic flow detection method

Among them, annular coil detection usually buried ring coil under the road, through the calculation of the vehicle through the coil circuit caused by the change in the resonant frequency of the coil, to achieve the traffic flow parameter detection, in the vehicle congestion, the workshop is small, the detection accuracy is very low, and the coil by temperature changes and subgrade problems and other factors, failure rate is high, More difficult to maintain, XXX.

toroidal coils

Ring-Type Coil detector is buried in the driveway under the ring-type coil, when the vehicle through the ring-type coil, so that the electromagnetic induction of the ring coil changes, resulting in resonance circuit resonant frequency changes, the computer through the resonant frequency of the sampling, the detector on the detection of whether there is a vehicle through or presence of judgment. Ring-Type Coil detector has the advantages of low cost, easy installation, high sensitivity, small climate impact, but in actual use, due to road construction, road deformation and other factors make the coil damage rate is high, replace installation and maintenance to enter the main road, affect transport, resulting in higher costs, The workload of maintenance is also very limited to the data extraction of traffic flow, generally only can detect vehicle speed, driving direction, vehicle classification and so on.

Geomagnetic monitor

Geomagnetic detector is a simple, economical and durable detector. His sensor is a permanent magnet rod, which is wrapped around the coil in the outside, and the probe is buried in the ground. When the vehicle passes through the probe, cutting the magnetic lines, creating an inductive electromotive force in the probe coil, amplifying and outputting a pulse, but the stationary vehicle does not produce output, so this is also the flaw of the geomagnetic detector. For the only requirement of recording the number of vehicles to and from the occasion, the geomagnetic detector is more appropriate, and for other traffic flow data detection is inadequate, you can see the application of geomagnetic detector is not wide.

Electromagnetic detection

The electromagnetic detector is a special type of geomagnetic detector that can detect moving vehicles and still vehicles. He is active detection equipment, it can detect two vehicles close to each other, the sensitivity is high, is very suitable as a count detection, but the electromagnetic detector on the vehicle edge positioning is not good, so it is seldom used to determine the occupancy and speed, the classification of the car is difficult to detect.

Microwave

The microwave detector consists of a transmitting antenna and a transmitting receiver. A transmitting antenna mounted on a gantry or on a roadside column, transmitting a microwave beam to the monitoring area. However, when the vehicle passes, the reflected wave will return to the antenna at different frequencies due to the Doppler effect, and the receiver of the detector detects the change of the frequency, thus determining the vehicle's passage or presence. Microwave detector has the characteristics of multi-detection area, can detect traffic volume, speed, occupancy and other traffic flow information, at present in the traffic detection also has a great advantage, and video detection compared to, its disadvantage is that can not provide visual surveillance capabilities, record traffic vehicles or the visual characteristics of the road. Therefore, microwave detectors are often used in conjunction with TV monitoring.

Ultrasonic

Similar to microwave detectors, ultrasonic detectors are also made using the principle of reflected echoes. The ultrasonic detector is detected by the ultrasonic generator reflected by the vehicle reflected by the ultrasonic echo to detect the vehicle, if the ultrasonic detector probe corresponding to the detection area of the vehicle through or exist, ultrasonic detector probe reflected out a bunch of ultrasound, will reflect back by the same probe received, By judging the difference in time between the signal and the original reflected echo signal, the judgment of vehicle passing or presence in the detection area is made. ' The ultrasonic detector has the installation does not need to destroy the road surface, is not affected by the road construction, the deformation, the detector position can move and so on the merit, its disadvantage is susceptible to the environment influence, when the wind speed is larger when the wave velocity will drift but cannot the normal detection, in addition detector probe under the person and object such as pedestrian umbrella, Bicycle groups can also produce reflective waves causing false tests.

Local Traffic condition detection