Gate Operators, Automatic Gate Inductive Loops (traffic loops) and Drive Surface Condition

What most people call traffic loops are actually called inductive loops.  They’re the most effective and reliable method and device for through or driveway vehicle detection, period.

How do they work?  Simply put it is a loop of wire with an extension cable connected to a detector.  The detector powers the wire loop causing a magnetic field that maintains a constant frequency that the detector monitors.  When a vehicle, large metal object, moves over the loop the frequency changes which is detected by the detector.  When the detector “detects” a presence it triggers a relay activation or “input” for an action on the gate operator. The input can be set for many different actions. Yes, there is more to it than what’s in this paragraph but if you understand in basic terms how they work, understanding what sales people and technicians say is less confusing.

Many variables effect loop performance and function. What we’d like to address here is the most frequent reason for loop failure and that’s poor condition of the drive surface.  Whether asphalt or concrete once the surface starts to crack and deteriorate loop problems are likely to occur.  If the loop wire is damaged in any way as the surface deteriorates, short or an open wire the loop will begin to intermittently fail. Most all loop detectors are designed to “fail safe” which means the gate will hold open and not close until the loop is repaired or replaced. These intermittent problems will most likely start to appear during wet weather and as the surface continues to deteriorate the problem will become more frequent until it fails completely.

Inductive loops in a good stable surface will last many years. We have loops that Mid-Atlantic Entry Systems installed over 20 years ago where the surface has remained in good condition that are in service to this day with no signs of trouble. There is no way to predict how long an inductive loop will last in a poor surface.  It depends on the amount of cracks and how much the surface is shifting.  For high security sites with inductive loops the condition of the drive surface is a critical preventive maintenance item.