A SIMOPS risk assessment fails long before anyone gets near the hazards it's supposed to catch. It fails when it's treated as a document to produce rather than a decision to make — a form completed after the schedule is fixed, rather than a process that shapes the schedule. On a site running several concurrent activities, that distinction is the difference between a control measure and a filing exercise.
What a SIMOPS risk assessment actually is
A SIMOPS risk assessment is a structured evaluation of whether two or more activities can run safely at the same time and place, and if so, under what controls. It differs from a standard task risk assessment or JSA because it isn't assessing one job in isolation — it's assessing the interaction between jobs: shared hazards, competing resources, and overlapping exclusion zones.
HSE's guidance on permit-to-work systems, HSG250, treats simultaneous operations as a specific case requiring its own controls beyond the individual permit — recognising that a permit written for a single task doesn't automatically account for what else is happening nearby. OEUK and predecessor industry bodies have published guidance on managing SIMOPS on UK offshore installations, and much of the vocabulary — SIMOPS matrix, interaction potential, concurrent activity register — comes from that body of practice rather than from statute. None of this is a legislative requirement in its own right; it sits under the broader duty to manage major accident hazards and to plan work safely, and an operator's safety management system will usually set out how SIMOPS assessments fit into that.
When the assessment gets triggered
Most SIMOPS assessments don't start with a hazard — they start with a schedule clash. Common triggers include turnaround and shutdown planning, where dozens of work packages compete for the same plant and the same permits; drilling or well intervention running alongside continued production; and construction or modification work happening adjacent to a live process area. The trigger point matters because it determines who raises the flag. On a well-run site, planning or scheduling teams surface potential clashes as the work-week schedule is built, rather than leaving it to the permit issuer to spot two crews converging on the same platform on the day.
Where activity schedules, permit systems, and isolation plans are held in separate places, this early screening is harder to do consistently — someone has to manually cross-reference three systems to see what's actually planned for the same area on the same shift. That's one of the practical arguments for visibility into simultaneous operations built into the permit system itself, rather than assembled after the fact.
Building the activity list from the schedule
The first real step is pulling together everything scheduled to happen in a given area and timeframe — not just permits already raised, but planned work still at the request stage, contractor mobilisations, and any standing activities like ongoing scaffold inspections or routine sampling rounds. This list needs to include activity type, location, duration, the permits or certificates each activity will need, and the crews and equipment involved. Missing an activity here isn't usually deliberate — it's more often that the activity was added to the schedule after the SIMOPS review was already done, which is why the assessment needs a defined point in the planning cycle rather than a one-off pass.
Screening for interaction, not just proximity
Once the activity list exists, each pair of activities gets screened for interaction potential across a few dimensions: spatial (do exclusion zones, laydown areas, or access routes overlap), temporal (do the activities coincide on the same shift or overlap during handover), resource (do they need the same crane, the same isolation, the same competent person), and competency (does running both at once put pressure on supervision or authorisation cover). Two activities can share a location without being incompatible, and two activities in different areas can still conflict if they draw on the same isolation or the same crane. This is where a permit interaction matrix earns its place — as a screening tool that flags which combinations need a closer look, not as the assessment itself.
Running the study session
Where screening identifies a genuine interaction, the next step is a structured SIMOPS study — a short workshop rather than a desk exercise. The people who need to be in the room are the Area Authority or duty holder with authority over the location, the permit issuer or Control of Work coordinator, discipline leads for each activity involved, and anyone responsible for the isolations or equipment the activities share. The session works through each identified interaction, agrees whether the activities can run concurrently at all, and if so, what additional controls — sequencing, physical barriers, standby supervision, communication protocols — make that acceptable. It's worth being explicit here: the output of this session is a decision, with named people accountable for it, not a checklist that gets ticked off.
A worked example: scaffold erection under a live crane lift
Take a hypothetical case. A scaffold crew is due to erect access scaffolding against a pipe rack that runs directly beneath a planned crane lift for a vessel replacement, and both jobs are scheduled for the same shift because the work-week plan treated them as unrelated. Screening flags the interaction on spatial and temporal grounds — the scaffold crew's working area sits inside the crane's lift radius. In the study session, the discipline leads confirm the lift can't be delayed without pushing the wider turnaround critical path, so the group agrees the scaffold erection is resequenced to start after the lift is complete and the load is landed, with the crane's exclusion zone physically barriered and the permit issuer holding both permits pending confirmation of sequence. That agreement then needs to be reflected in both permits before either is issued — not left as a note from the meeting.
Turning the output into permit conditions
A SIMOPS assessment that produces a report nobody reads at shift handover hasn't achieved much. The controls agreed in the study need to show up as conditions on the actual permits — sequencing notes, cross-references between the two permit numbers, holds tied to confirmation from the other work party — so that whoever accepts the permit on shift sees the constraint, not just the person who sat in the workshop. This is also where contractor competency and authorisation checks matter: a control that depends on a specific supervisor being present only works if the permit system can confirm that person is actually on site and authorised for the shift, a point we've covered in relation to contractor permit management more broadly.
When evaluating a permit-to-work system, it's worth asking the vendor to demonstrate how a SIMOPS interaction gets linked across two live permits, and what happens if one permit is suspended or extended after the other has already been accepted. If the answer involves someone remembering to check a spreadsheet, the SIMOPS assessment is only as good as whoever's on shift that day.
If you're reviewing how SIMOPS assessments feed into your Control of Work process, we can walk through your current planning and permit workflow to see where the two are — or aren't — actually connected.