🎓 Lesson 17
D5
STEP Analysis for Task-Level Ergonomic & Cognitive Hazards
STEP Analysis is a simple checklist to spot physical and mental hazards that workers face while doing a specific blasting or mining task—like drilling, loading explosives, or inspecting blast areas.
🎯 Learning Objectives
- ✓ Analyze a blast crew’s pre-shot inspection task using the STEP framework to identify at least three distinct ergonomic or cognitive hazards
- ✓ Explain how environmental stressors (e.g., noise >105 dB, glare, vibration) degrade situational awareness during explosive handling
- ✓ Apply STEP findings to redesign a drill rig operator workstation to reduce static postures and visual scanning load
- ✓ Evaluate the adequacy of PPE integration within the 'Tools & Equipment' domain using ISO 13732-1 and ANSI/ASSP Z590.3 criteria
📖 Why This Matters
In underground and surface mines, over 32% of recordable injuries involve musculoskeletal disorders (MSDs) or human error linked to cognitive overload—not equipment failure. A 2022 ICMM report found that 68% of near-misses during blast preparation stemmed from unaddressed STEP-domain gaps: cramped cab layouts (Space), poorly balanced detonator testers (Tools), low-light misreads of delay timings (Environment), or fatigue-induced verification lapses (People). Mastering STEP helps you catch these before they trigger injury, misfire, or regulatory noncompliance.
📘 Core Principles
STEP is not a standalone model—it integrates with ISO 6385 (Ergonomic Principles), ISO 13408 (Cognitive Task Analysis), and MSHA Part 46/48 training requirements. Each domain maps to physiological and psychological stress pathways: Space assesses anthropometric fit and movement constraints; Tools & Equipment evaluates interface design, weight distribution, feedback clarity, and automation transparency; Environment quantifies sensory load (noise, thermal, illumination, air quality, vibration); People examines workload, training alignment, fatigue state, and team coordination fidelity. Critically, STEP requires task decomposition—e.g., 'loading ANFO into borehole #7' is one STEP unit, not 'blasting' as a whole—and demands direct observation, not just interviews or checklists.
📐 Cognitive Load Index (CLI)
The Cognitive Load Index estimates mental demand during time-critical tasks like explosive verification. It combines environmental distraction, interface complexity, and procedural novelty into a single normalized score. Values >7.0 indicate high risk of attentional capture or omission errors.
Cognitive Load Index (CLI)
CLI = E + T + P + SQuantitative estimate of total cognitive demand during a discrete task step, where each component is scored 0–3.5 based on validated severity anchors.
Variables:
| Symbol | Name | Unit | Description |
|---|---|---|---|
| E | Environmental Load Score | dimensionless | Summed score for noise, lighting, thermal stress, vibration, and air contaminants (per ISO 13732-1 and ISO 7243) |
| T | Tools & Equipment Load Score | dimensionless | Scored for interface complexity, feedback clarity, physical effort, and automation transparency (per ISO 9241-210 and ANSI/HFES 100) |
| P | People Load Score | dimensionless | Reflects fatigue, training adequacy, experience level, and team coordination fidelity (per NASA-TLX subscales and Fatigue Avoidance Scheduling Tool [FAST] inputs) |
| S | Space Load Score | dimensionless | Assesses anthropometric mismatch, static posture duration, reach envelope violations, and mobility constraints (per ISO 14738 and EN 1005-4) |
Typical Ranges:
Low-risk office-based planning task: 1.0 – 2.5
Standard drill rig operation (day shift): 3.0 – 5.5
Post-blast hazard verification in adverse conditions: 6.0 – 9.5
💡 Worked Example
Problem: Drill-blast foreman verifies electronic detonator delays in an open-pit blast ring under rain (reduced visibility), 98 dB(A) dragline noise, and uses a legacy handheld tester requiring 7 button presses per device with no audio confirmation. Procedural familiarity rating = 3/5 (new software update 2 weeks ago).
1.
Step 1: Assign scores: Environment = 3.2 (rain + noise + glare), Tools = 2.8 (7-step interface, no audio), People = 1.5 (moderate familiarity), Space = 0.5 (standing on uneven gravel, moderate reach), Total = 3.2 + 2.8 + 1.5 + 0.5 = 8.0
2.
Step 2: Normalize to 10-point scale: CLI = 8.0 (already scaled per ISO/TR 16982 guidance)
3.
Step 3: Compare to threshold: CLI > 7.0 → high cognitive load; recommend voice-assisted verification and noise-canceling headset.
Answer:
The result is 8.0, which exceeds the safe threshold of 7.0 and indicates urgent need for interface and environmental controls.
🏗️ Real-World Application
At Newmont’s Boddington Mine (WA), STEP analysis of the 'post-blast fume clearance check' revealed that inspectors spent 42 sec average per borehole verifying ventilation due to: (1) Space: confined access hatches forcing kneeling postures; (2) Tools: analog gas detector requiring manual zeroing and dual-scale reading; (3) Environment: 45°C cab interior + 112 dB diesel exhaust masking alarm tones; (4) People: rotating crews with <3 shifts of site-specific training. Redesign included widened hatches, Bluetooth-enabled digital sensors with spoken CO/H2S alerts, and thermal-acoustic shielding—reducing verification time by 63% and eliminating two near-misses in Q3 2023.
🔧 Interactive Calculator
🔧 Open Hazard Identification & Risk Assessment Calculator📋 Case Connection
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