How does the system know the runway is occupied?
Sensors report each runway zone as free or occupied, and the result goes to the tower, the ALCMS and the runway status lights.
Runway occupancy sensing detects whether an aircraft or vehicle is on the runway. The runway is divided into zones, and sensors such as in-pavement loops, radar or cameras report each zone as free or occupied. Occupancy logic turns the sensor data into that status and passes it on.
The status goes to the tower display, where it can raise an alert, and to the ALCMS. Where the airport has them, the ALCMS, or the status-light control system it interfaces with, uses it to switch runway status lights such as runway entrance lights and take-off hold lights, so a crew or driver about to enter or cross sees red while the runway is in use. A sensor fault must show on the tower display and not leave the lights in a false state; the fail-safe state of the lights on a fault is set in the system design and agreed with ATC. The status lights are an extra safety layer behind the ATC clearance, not a replacement for it. Occupancy sensing is the logic, and surface movement radar is one of the sensors that can feed it.
Frequently Asked Questions
Q1What is runway occupancy sensing?
A system that detects whether an aircraft or vehicle is on the runway and reports the runway, or each zone of it, as occupied or free. The result goes to air traffic control and, where fitted, to the lighting control system.
Q2How is runway occupancy detected?
By sensors such as inductive loops in the pavement, surface movement radar, cameras or other detectors. The runway is split into zones, and each zone reports its own status.
Q3What does the system do with the occupancy status?
It shows the status on the tower display, can raise an alert when a crossing or entry looks unsafe, and where installed drives runway status lights such as runway entrance lights and take-off hold lights.
Q4How does it connect to the AGL system?
The occupancy processor sends the zone status to the ALCMS, or to the status-light control system the ALCMS interfaces with, which switches the status lights through their control circuits. A sensor fault should show on the tower display and not leave the lights in a false state. The fail-safe state of the lights on a fault is set in the system design and agreed with ATC.
Q5Is runway occupancy sensing the same as surface movement radar?
No. Surface movement radar is one sensor that can feed occupancy sensing. The occupancy function is the logic that turns sensor data into occupied or free by zone and acts on it.
See It. Understand It. Then Learn How to Engineer It.
Recognising an AGL system visually is the first step. The next step is knowing how to design, install, test, commission and maintain them correctly.
Build Practical AGL Engineering Skills
Go deeper with structured training from Precision AGL Academy, covering:
Learn how each light, sign and circuit works as part of a complete airport lighting system, not just as an isolated diagram.