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By Mr. Yuan Shaosong
For reasons that are widely known, people have been seeking the replacement of loop detectors in the last ten years, which saw the emerging of non-contact detecting methods such as video, microwave, infrared, ultrasonic, acoustic, magnetic, etc. To this day, however, loop detectors remain the most widely used detecting technology. The reason is that it is thought more reliable and accurate than the latecomers. The wide range of non-contact technologies could overcome the shortages of the contact detectors like loop detectors to some extent, such as no need to damage the road surface and close the lane, low installation and maintenance costs. But all these technologies have their limitations, which their manufacturers are reluctant to mention. In addition, accepted standards and test data have not been established, making it hard for users to make choice.
In the 1990s, field test reports were released by some research institutes in the US who undertook the tests of various vehicle-detecting technologies. Among them, the most noticeable was the tests by the Hughes Aircraft and Let Propusion which were sponsored by FHWA as well as the tests undertaken by the California State Polytechnic, MinnDOT and Texas Transportation Institute,TTI. The results of these reports showed that all the non-contact detectors have their problem, which will directly influence the detecting accuracy.
How will these shortages be overcome? Until the question is answered, the inductive loop detecting technology will continue to dominate the market for a long time. Under such circumstance, other detecting products only survive a limited market space. Some detecting products are destined to become history. They will be eliminated by the market. Whereas other detecting technologies like video and microwave, with the expansion of use scope and frequent technical innovations, will be more widely employed.
In fact, compared with the inductive loop detecting technology, which features accurate counting, reliable performance and weatherproofing, the performance of RTMS (remote traffic microwave sensor) is equally good. When RTMS is installed over the lane, it shows excellent performance in accurately detecting the speed and traffic flow and will not be influenced the environment. For the description and evaluation of RTMS, please see the test reports of Hughes Aircraft and Texas Transportation Institute,TTI.
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