If you receive construction emails from us, you might know that we’ve installed vehicle detector loops at intersections with traffic signals. But if you’re like most people, traffic lights, and their various components [what are vehicle detector loops, anyway?] are probably one of those subjects you don’t give a lot of thought to. So next time you’re waiting for that light to change, here’s a primer on vehicle detector loops, and why you’ll be glad we’re installing them as part of our projects.
To begin with, vehicle detector loops [the technical term is “inductive-loop vehicle detectors”] are flat, loose coils of wire covered in light plastic, which are buried in the asphalt under the lanes at an intersection.
In York Region, most of our vehicle detector loops are approximately 4 metres square, and extend from the pedestrian crosswalk and across the stop bar [the wide white line going across each traffic lane at intersections] for approximately 15 metres.
The point of a vehicle detector loop is to detect when vehicles are sitting at the intersection. Vehicle detector loops are able to do this through a process of magnetic induction, which results when metal objects [i.e., vehicles] are nearby. Put simply, the presence of the vehicle results in a change in the magnetic field of the loop. This change is detected by the traffic signal controller [a large box located near every signaled intersection], which in turn sends a message to the traffic signal to begin turning from red to green.
York Region owns and or maintains 848 signalized intersections [traffic lights occasionally are used in other settings such as single lanes through construction zones]. Most of York Region’s traffic loops are located on side street lanes, in left turn lanes to activate advanced left turn signals, and on rapidways to detect transit vehicles.
The Region also uses “Matrix” vehicle detection, a pole-mounted system using radar imaging, in construction zones where lanes are moved, and where it’s problematic to install traffic loops. For more information on the technology of traffic signals, check out york.ca/intersections.
Ultimately, traffic loops improve the performance of an intersection, helping traffic flow by detecting you better.