A vehicle loop detector is a buried wire loop that senses a car by the change in inductance as metal passes over it. Paired with a barrier gate, it automates arrival detection and prevents the boom from closing on a vehicle.

How a loop detector works

The loop is cut into the pavement and tuned to the detector card. When a vehicle enters, inductance drops and the detector sends a relay signal to the barrier controller. Two common configurations are a single loop (presence only) and a double loop (presence plus direction).

Why integrate loops with barriers

• Safety: the boom will not lower while a car occupies the exit loop.
• Automation: the gate opens on arrival without a manual button.
• Counting: double loops can count entries and exits for occupancy data.

Installation notes

Loops are placed just before and just after the boom. Saw-cut loops must be sealed properly and kept clear of rebar where possible. For sites where cutting pavement is impossible, wireless or radar presence sensors are an alternative.

For a full selection framework, see our barrier gate guide and the applications overview.

Frequently Asked Questions

What does a vehicle loop detector do?

It senses a vehicle by a change in inductance as metal passes over a buried wire loop, then signals the barrier controller.

Why use a double loop instead of a single loop?

A double loop adds direction sensing and vehicle counting, while a single loop only confirms presence in one spot.

Can I install a loop where I cannot cut the road?

Yes. Where saw-cutting is impossible, wireless or radar presence sensors can replace inductive loops.