Several monitoring methods commonly used in traffic supervision
Several monitoring methods commonly used in traffic supervision
There are many places and roads in China, and the traffic management departments of various cities and regions also have diversity in purchasing products. On the one hand, it is inseparable from the performance indicators of the equipment itself, and it is also closely related to the equipment cost, local road conditions, and local traffic regulation policies. At present, the common regulatory products in China are as follows:
Ground buried induction coil (or induction rod)
This method is classic and the detection effect is good. For example, southern China, such as Shanghai, Guangdong, and other regions often use this method. Determine whether the vehicle exceeds the speed limit according to the speed of the vehicle passing through the parallel coil, and take photos for evidence. The disadvantage of this detection method is that the construction amount of the induction coil buried on the ground is large. Once the road surface is changed, the coil needs to be buried again. In addition, the maintenance work of the coil is huge on the road surface in high latitude thaw period, low latitude summer, and places with poor road surface quality.
Video detection
This method tracks the process of illegal vehicle behavior through the analysis of continuous video images, and captures illegal vehicles through analysis and control photography. The advantage of this system is that it is not limited by the road surface conditions, and it does not need to damage the road surface during installation, or to bury sensing loops under the road surface. It is a new generation of road vehicle detection method by erecting cameras above the road to detect traffic data. The disadvantage of video is that it is difficult to identify moving vehicles. On the one hand, it is necessary to have a fast enough shutter (at least 1/3000PX) and a sufficient number of pixels and image algorithms when shooting high-speed moving vehicles; On the other hand, the speed of vehicles is generally slow at intersections, crossings and entrances and exits of expressways. The most common violations are red light running, lane merging violations and wrong lane selection, which do not require radar to cooperate with the expressway video camera The monitoring purpose can be achieved by using a slower shutter. In addition, video technology is affected by light and weather.
Microwave radar
As mentioned above, different from video detection, intersections are usually multi lane and have the complexity of multi vehicles and multi pedestrians. It is also difficult to detect illegal vehicles at intersections with microwave radar only using Doppler effect. For high-speed roads with fast speed and single direction, microwave radar is the best partner to cooperate with high-speed cameras at present. When high-speed cameras receive high-speed moving vehicles detected by microwave radar, they quickly enter a fast capture state, Cooperate with the high-speed shutter to obtain evidence against regulations. The mainstream product in the world is radar with high-speed camera to shoot overspeed.
Ultrasonic testing
The principle of ultrasonic distance measurement is mainly used. The service life of the ultrasonic sensor head is only a few weeks at most in the dusty and harsh environment at the intersection, so the detection method is not applicable.
Infrared detection and laser detection
There are similarities between infrared and laser detection. Due to the laser measurement behavior, it is feasible in theory and the detection process is quite high. However, compared with microwave radar, it also faces the impact of many intersections, roads, vehicles and pedestrians, and the point measurement efficiency cannot meet the regulatory requirements, The most important thing is that the damage of the laser beam to the human body, mainly the human eye, is a particularly serious problem. In Europe, America and other countries, the performance indicators of the laser speed measuring instruments must not only meet the international safety standards, but also must be manually controlled in use to avoid injury to many people's eyes. In Japan, the use of laser detection equipment is strictly prohibited, so laser detection is better in theory, but the safety problems in the use process have not been solved yet.
Common installation methods and working principles of surveillance cameras
In fact, the surveillance camera at the intersection can take photos of the driver running the red light through many technologies. There is no unified standard and method in this regard, which is completely dependent on the winning construction company. Generally, it can be triggered by radar, induction coil or image recognition. When using the radar triggered photographing method, when the red light is on, a radar area is formed in front of the parking line. When a car passes, start the electronic shutter to take a picture. At this time, the radar speed detector may work. When the induction coil is used for taking photos, the induction coil is buried under the road surface during road construction. When a car runs the red light, the induction coil car starts the electronic shutter to take photos. When using image recognition technology, take the white line on the ground as the warning area. When a vehicle runs through the red light, the white line on the ground is blocked, and the camera is triggered. Due to the different technologies, no device can predict the red light. Unlike speed measurement, which only uses radar laser technology, radar speed detector can completely predict speed detection.
