Safety Critical Task Analysis (SCTA) UK

We identify and assess human error potential in safety-critical tasks using structured methodologies aligned with HPOG, IOGP 454, and HSE guidance. Our SCTA programmes support COMAH compliance, safety case submissions, and operational improvement initiatives.

Every SCTA engagement is led by Dr. Chizaram Dagogo-Nwankwo, Chartered Ergonomist (C.ErgHF, CIEHF), with published peer-reviewed research in human factors and accident causation in high-hazard industries.

What is Safety Critical Task Analysis?

Safety Critical Task Analysis is a structured method for identifying the tasks within an operation where human error could directly cause or contribute to a major accident event. It goes beyond conventional hazard identification by examining not just what could go wrong, but the human performance conditions — cognitive demands, time pressure, interface design, procedural clarity — that determine how likely an error is and how recoverable it is if it occurs.

SCTA is not an audit of compliance. It is an analysis of the interaction between people, tasks, and systems under real operating conditions. The output is a prioritised register of critical tasks with documented error modes, contributing factors, and recommended controls.

In the UK, SCTA is referenced in HSE Research Report RR1189, the Energy Institute's guidance on human factors in process safety, and IOGP Report 454. It is a core component of demonstrating human factors competence in COMAH safety cases and SEMSCA submissions.

Who needs this service

1. COMAH-regulated sites
   Upper and lower tier COMAH sites are expected by the HSE to demonstrate that human factors have been considered in the identification and management of major accident hazards. An SCTA provides the documented evidence of that consideration. Without it, safety case reviews and competent authority inspections routinely identify human factors as a gap.
2. Offshore and onshore oil and gas operators
   IOGP 454 sets the expectation for human factors engineering across the project lifecycle. SCTA is the primary tool for identifying and managing human error in operations, maintenance, and emergency response tasks. Operators preparing for SEMSCA, DCR compliance, or internal safety case review use SCTA to demonstrate systematic human factors assessment.
3. Chemical and process manufacturers
   Facilities handling hazardous substances where a single operational error could trigger a loss of containment, fire, or explosion. SCTA identifies which tasks carry the highest human error risk and what controls reduce that risk to as low as reasonably practicable.
4. Energy and utilities operators
   Power generation, water treatment, and energy distribution facilities where safety-critical tasks are carried out under time pressure, shift patterns, and with ageing plant. SCTA is used to assess task demands against operator capabilities and identify where the gap is widest.
5. Organisations following a major incident
   Where a serious near miss or incident has occurred and the investigation has identified human factors as a contributing cause, SCTA provides the structured follow-up analysis that regulators expect to see in the corrective action plan.

What our SCTA programme includes

1. Task identification and criticality screening
   We work with your operations and safety teams to identify the full population of tasks within scope, then apply a criticality screening to focus the detailed analysis on those where human error could directly initiate or fail to recover a major accident scenario.
2. Hierarchical Task Analysis (HTA)
   Structured decomposition of each critical task into sub-tasks and operations. Documented in a format suitable for safety case submission, regulatory review, and as a living reference for training and procedure development.
3. Human Error Identification (HEI)
   Systematic identification of the error modes associated with each task step, using structured techniques aligned with HSE RR1189 and IOGP 454. Error types categorised by omission, commission, timing, sequence, and selection errors.
4. Performance Influencing Factor (PIF) assessment
   Assessment of the factors that affect the likelihood and severity of each identified error: procedure quality, workload, time pressure, workplace environment, equipment and interface design, communication, training, and supervision. PIFs documented with current adequacy rating and recommended improvements.
5. Risk ranking and prioritisation
   Each identified error mode ranked by likelihood and consequence. Output aligned with the existing risk matrix where one exists, or developed as a standalone register. Prioritised action list with recommended controls at the task, procedure, and system level.
6. SCTA report and deliverables
   A formal written SCTA report suitable for inclusion in a COMAH safety case, DCR submission, or internal safety management system. Report format aligned with regulatory expectations. Includes summary findings, full task analysis documentation, PIF assessment, and prioritised recommendations.

When to commission an SCTA

SCTA is typically commissioned at four points in an operation's lifecycle:

1. New facilities and major modifications — during FEED or detailed design, where the findings can still influence system design, interface layout, and procedure development before construction.
2. Pre-startup safety reviews — as part of the final safety case submission or COMAH notification, to demonstrate that human factors have been considered in the operational hazard identification.
3. Periodic revalidation — following changes to operations, staffing, procedures, or plant that may have altered the human performance demands of critical tasks since the last analysis.
4. Post-incident investigation — where a serious event has occurred and the root cause analysis has identified human factors as a contributing element. The SCTA provides the structured evidence base for the corrective action programme.

The research basis for our methodology

Our SCTA methodology draws on peer-reviewed research into accident causation in high-hazard industries, including published work using the HFACS-OGI framework to analyse human factors in oil and gas accidents. That research consistently shows that critical task failures trace back to upstream conditions — procedure design, workload, interface quality, supervision — rather than individual operator error.

This finding shapes how we conduct task analysis. We don't treat human error as an endpoint. We treat it as a signal pointing to system conditions that can be identified, quantified, and controlled.

Published research is available at nancheez.co.uk/publications.

Frequently asked questions

What is the difference between SCTA and a HAZOP?
A HAZOP (Hazard and Operability Study) identifies deviations from design intent in process systems, typically using guide words applied to process parameters. SCTA examines the human performance demands and error potential within the tasks people carry out to operate, maintain, and respond to those systems. The two methods are complementary; SCTA is often commissioned alongside or after a HAZOP to address the human factors dimension that HAZOP doesn't fully cover.

Is SCTA a regulatory requirement under COMAH?
SCTA is not named as a specific requirement in the COMAH Regulations 2015. However, the Control of Major Accident Hazards regulations require operators to demonstrate that major accident hazards have been identified and controlled, and that human factors have been considered. The HSE's competent authority routinely identifies the absence of structured human factors task analysis as a gap in safety case submissions. SCTA is the methodology that closes that gap.

How long does an SCTA take?
Duration depends on the number of critical tasks in scope and the complexity of the operation. A focused SCTA covering 10 to 15 critical tasks in a defined operational area typically takes four to eight weeks from scoping to final report. A full-facility SCTA for a complex process plant may take three to six months. We scope each engagement individually after an initial conversation.

Can SCTA findings be integrated into our existing safety management system?
Yes. SCTA outputs — the task register, PIF assessments, and recommended controls — are designed to feed directly into procedure development, training needs analysis, competence management systems, and safety case documentation. We can support that integration as part of the engagement or provide the documentation in a format your team can work with independently.

Do you carry out SCTA for digital and control room environments?
Yes. Control room SCTA addresses the specific human performance demands of alarm management, HMI operation, and process control tasks. This is often commissioned alongside our Human Factors in Design and Digital Systems service where control room design or upgrade is also in scope.

Discuss a project

SCTA engagements are scoped individually. Tell us about your operation, the regulatory driver or business need, and your timeline and we'll come back within two working days with a proposed approach.