Alberta OHS Code s.267: operating with an obstructed view

Most conversations about equipment safety in Alberta start in the wrong place. They start with what a contractor is willing to buy, rather than with what the Code already obliges them to do. The relevant rule is narrower and more specific than most people expect, and it names the technology option explicitly.

The rule in one sentence

Part 19 of the Alberta Occupational Health and Safety Code covers powered mobile equipment. Section 267 deals with the situation every operator faces daily: the machine is about to move in a direction the operator cannot see clearly.

When that is the case, the employer must ensure one of three things is in place. Not a general commitment to safety, and not a policy document. One of three specific controls.

The three options in s.267(1)

An automatic audible warning device. The Code qualifies this: the warning must be loud enough to be heard above other noise in the immediate area.

An alternate warning device or method appropriate to the hazards.

An automatic stopping system. The Code notes this system may use motion, thermal or other detectors.

That third option is the one worth sitting with. The Code does not treat an automatic stopping system as an optional upgrade above a backup alarm. It treats it as a compliance route in its own right, equal in standing to the alarm most fleets already rely on.

What counts as an automatic stopping system

The Code is deliberately non-prescriptive here, noting only that such a system may use motion, thermal or other detectors. It does not mandate a technology. What distinguishes this option from the other two is not the sensor but the response: the system acts on the machine rather than relying on a person to react.

In practice that means a system should be able to answer three questions on your site, not in a brochure:

1. What does it detect, and can it tell a person from a pile of material or a parked truck? Distance matters here, because a system that only detects motion cannot distinguish a worker two metres behind the machine from one 20 metres away.
2. What does it do when it detects something, and how quickly? A warning is a different control from a stop.
3. What happens when it cannot see, or when a sensor is obscured by dust or damage? A system that fails silently is worse than no system, because the crew has stopped compensating for the risk themselves.

If none of the three is practicable: s.267(2)

The Code anticipates that none of the three options may be workable, and sets out what has to happen instead. The precautions it lists include a detailed inspection of the travel path by the equipment operator, direction by a designated signaller or other worker who is in continuous view of the operator and has a complete view of the area the equipment will move into, direction by a traffic control or warning system, or ensuring all other workers are removed from the area.

This is where the signaller requirement people usually cite actually lives. It is a fallback, not the primary rule, and its conditions are demanding: continuous view of the operator, and a complete view of the area the machine is moving into. A person half-watching from the side of the pad while doing something else does not meet that description, however common the arrangement is.

Section 259: keeping people and machines apart

Section 267 is about the moment of movement. Section 259 is about the layout that produced the moment. It requires employers, where reasonably practicable, to designate walkways that separate pedestrians from areas where powered mobile equipment operates. Where that is impracticable, it allows other effective means, with speed limits, acknowledgment protocols and high-visibility clothing among the examples.

Read together, the two sections describe a hierarchy that mirrors standard safety practice: separate people from machines first, and control the interaction where separation is not possible.

A practical way to audit your own fleet

• For each machine class, list the directions of travel where the operator's view is obstructed. Be honest about the tail swing on excavators and the rear quarters of loaders.
• For each of those, write down which of the three s.267(1) options you are relying on today.
• Where the answer is the backup alarm, ask whether it is genuinely audible above the noise on that particular site, with the hearing protection your crews actually wear.
• Where the answer is a signaller, check the arrangement against the wording in s.267(2): continuous view of the operator, complete view of the area.
• Record the assessment. In an investigation the question is rarely whether you had a policy. It is what control was in place on that machine, that day, in that direction.

Where Sentinel fits

Sentinel is built as the third option. Stereo cameras measure distance rather than motion alone, so the system knows how far away a person is. When someone enters a danger zone the operator is warned, and if they do not respond the machine automatically stops. The decision is made on the device, so it does not depend on a network connection on site.

That does not remove your obligations under Part 19, and no supplier should tell you it does. What it changes is which of the three options in s.267(1) you are relying on, and whether that control depends on human vigilence and reflexes.

See how the detection and stop work, or read why struck-by incidents keep happening despite these controls being standard for decades.