Induction loop detector systems crosstalk

Abstract

Reducing congestion on U.S. urban roadways has become a top priority of state departments of transportation nationwide. The development and construction of freeway management systems have recently begun to help reduce this problem. Today, modem traffic control systems are necessary to obtain maximum possible efficiency from our freeway systems. A major component of freeway management systems is the induction loop detector. This research effort evaluated the methods by which crosstalk could be controlled effectively in a freeway management situation and, thereby, make the most efficient use of induction loop detectors. Tests were conducted to evaluate the distance at which no crosstalk was observed between two adjacent induction loop detectors. Tests were also conducted to measure the potential of crosstalk within a controller cabinet and in twisted and untwisted lead wires. As a part of this ongoing research, attention was also given to determine the distance of no spillover at detector unit sensitivity-settings of Low, Medium, and High. All of these tests were performed using two different types of detector units, viz., Detector Systems stand-alone detector units, and Naztec rackmounted units. It was observed that a distance of 48 inches (1.21 meters) between the edges of two adjacent induction loop detectors eliminated crosstalk between them. The tests also indicated that there was no crosstalk on twisted and untwisted lead wires. Furthermore, there was no measurable evidence of crosstalk in the controller cabinet. Three different speeds of 20, 40, and 60 mph (32, 64, and 97 km/h, respectively) were used to study the detection zone between two loop detectors connected to the same detector unit. It was observed that, if two 6 feet-by-6 feet (1.83 by 1.83 meters) loop detectors are placed at a spacing of 20 feet (6 meters) from lead-edge to lead-edge, they act as a single long loop detector. It has been established that the use of multiple small loops is more advantageous than using a single long loop detector.