FAQs • Manhattan • CivicEngage

How does an inductive loop work?: Inductive loops are either diamond shaped or rectangular loops of wire generally sawed into the surface of the pavement. The wire is stranded copper wire in a weatherproof tubing. A very small amount of electricity flows through the wires, creating a magnetic field. When a vehicle pulls over the loop, it causes a disruption in the magnetic field. A detector in the controller cabinet detects the disruption and sends a signal to the controller indicating the presence of a vehicle.

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Traffic - Detection of Vehicles at Traffic Signals

1. What method does the city use to detect vehicles at traffic signals?: There are two types of vehicle detection methods we use. The most common method is inductive loops, and the other method uses video detection.

2. How does an inductive loop work?: Inductive loops are either diamond shaped or rectangular loops of wire generally sawed into the surface of the pavement. The wire is stranded copper wire in a weatherproof tubing. A very small amount of electricity flows through the wires, creating a magnetic field. When a vehicle pulls over the loop, it causes a disruption in the magnetic field. A detector in the controller cabinet detects the disruption and sends a signal to the controller indicating the presence of a vehicle.

3. Does the weight of my vehicle matter?: Yes and no. Since the loop wires do not weigh the vehicle, the answer is no. However, the larger the metal mass, the easier it is for the loops magnetic field to be disrupted. The smaller vehicles mass of motorcycles and bicycles makes it very difficult to detect.

4. What has the city done to improve detection of motorcycles and bicycles?: The city installs the loop wire in a diamond fashion. A typical four-section diamond loop contains more than 400 feet of loop wire. This method creates a more sensitive magnetic field and has improved the ability of the signal to detect the presence of motorcycles. The most effective way for motorcyclists to improve detection by the signal is to stop over the intersection of two of the diamonds. Bicycles do not have enough mass to cause a disruption in the magnetic field.

5. What is video detection?: This is the newest technology used by the city. Video cameras, such as those at Denison Avenue and Kimball Avenue, are installed on the traffic signal mast arms. The camera recognizes vehicles entering a designated area of the street and sends a message to the signal controller indicating the presence of a vehicle. This system does an excellent job of detecting the presence of motorcycles and bicycles.

6. How do I report a traffic signal malfunction?: You can report a traffic signal issue with our online Report It! feature. You can also call 785-587-4541.