DEVB TC(W) No. 3/2023, Annex A 5(12)(e)
Mobile plant anti-collision: danger zone alert for excavators and cranes
Clause 5(12)(e) of DEVB TC(W) No. 3/2023, Annex A, requires an automated warning system on all mobile plant, with sensors giving 360 degree cover of a danger zone generally at least 2 m from any part of the machine. A person entering it triggers a cab warning, a siren of at least 100 dB and an alert to supervisors. Kodifly fits and runs it.
What the circular requires, and where it is mandatory
The circular asks for an automated warning system on all mobile plant, including excavators, crawler cranes and mobile cranes. It warns the operator, and any person who steps into the danger zone, of the risk of being run over or hit by moving parts (clause 5(12)(e)). The Safety Officer sets the danger zone by risk assessment. The Buildings Department and CIC name it the unsafe acts and dangerous situation alert for the mobile plant operation danger zone.
The requirement now reaches private works. Since July 2024 the Buildings Department attaches conditions to building works above HK$30 million that use mobile plant and tower cranes, so registered contractors must use the 4S Mobile Plant Alert System and Tower Crane Alert System. Since July 2025 it also covers demolition, excavation and lateral support, foundation and site formation works (LCQ13, 24 June 2026).
Requirements in Annex A, clause 5(12)(e), mobile plant
| Topic | Requirement |
|---|---|
| Scope | All mobile plant operating on site, including excavators, crawler cranes and mobile cranes. |
| Sensor cover | Enough sensors on the chassis and movable superstructure for full 360 degree cover of the danger zone perimeter. |
| Danger zone | Set by the Safety Officer from the risk assessment. Generally not less than 2 m from any part of the plant. |
| In the cab | A warning light on the dashboard and a spoken message by speaker or headphone telling the operator to stop all plant operation. |
| At the machine | A roof siren with flashing red light and continuous warning of at least 100 dB. It switches off when the person leaves the zone. |
| Alert message | SMS or in-app pop-up to site supervisors and the Safety Officer, recorded at the platform with the date and time of the encroachment. |
| Video clip | Where specified, a clip from 15 seconds before the encroachment to 10 seconds after the person leaves. |
| Accuracy | At least 90% accuracy, proved by a live trial (clause 5(2)). |
When someone enters the danger zone
Detect
A sensor on the chassis or superstructure picks up a person inside the zone.
Warn the operator
A dashboard light flashes and a spoken message says stop all operation.
Warn the person
The roof siren sounds at 100 dB or more with a flashing red light.
Alert
Supervisors and the Safety Officer get an SMS or pop-up with the date and time.
Clear
When the person leaves the zone, the signals switch off automatically.
How Kodifly supplies, installs and runs it
Sensors, cab unit, siren and platform link are fitted to each machine as one project.
Devices, software and installation together
Sensors for 360 degree cover on each machine
Cab light and spoken warning for the operator
Roof siren and flashing red light
Danger zones set with the Safety Officer
Live trial to show the accuracy the clause asks for
Alerts to supervisors and the Safety Officer
Event record on the platform
Mobile plant anti-collision, answered
What does the circular require for mobile plant?
An automated warning system on all mobile plant, with 360 degree sensor cover of the danger zone, a cab warning, a roof siren of at least 100 dB and an alert to supervisors (Annex A, clause 5(12)(e)).
How big is the danger zone?
The Safety Officer decides it from the risk assessment. It should generally be not less than 2 m from any part of the mobile plant (clause 5(12)(e)).
How loud must the siren be?
At least 100 dB, with a flashing red light, switching off automatically when the person leaves the danger zone (clause 5(12)(e)).
Is a video clip required?
Only where the contract specifies it. The clip runs from 15 seconds before the encroachment to 10 seconds after the person leaves (clause 5(12)(e)).
Is it mandatory on private building works?
Yes for building works above HK$30 million that use mobile plant. The Buildings Department imposes it as a condition, and since July 2025 it also applies to demolition, excavation and lateral support, foundation and site formation works (LCQ13, 24 June 2026).
Is there funding for plant owners?
The Construction Innovation and Technology Fund extended eligibility to local mobile plant and tower crane rental companies in 2024, with a ceiling of HK$7.5 million per company for danger zone alert systems (LCQ13, 24 June 2026).
Related guides
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