Safety

Construction is one of the most dangerous industries. Learn hazard identification and risk assessment, the hierarchy of controls, major hazards (falls, excavations, cranes, electricity, confined spaces), PPE, permits to work, safety metrics (LTIFR) and safety management systems.

Every year thousands of construction workers die from falls, collapsing trenches, falling objects and machinery. Almost all of these accidents are preventable with planning, engineering controls and a strong safety culture.

Engineers influence safety most at the design and planning stage — designing out hazards is better than managing them on site.

An analogy

Safety is like layers of Swiss cheese: each layer (design, procedures, training, PPE) has holes, but stacking layers makes it unlikely that a hazard passes through all of them.

Major construction hazards

Falls from height (the leading killer), struck by falling objects or vehicles, trench and excavation collapse, electrocution, caught-in machinery, crane and lifting failures, confined spaces, fire, manual handling, silica dust and noise.

Hierarchy of controls

Elimination (design out the hazard, e.g. prefabricate at ground level) → substitution → engineering controls (guardrails, trench boxes, edge protection) → administrative controls (permits, training, exclusion zones) → PPE (helmets, harnesses, boots, gloves, eye/ear protection) as the last line.

Risk assessment and permits

Identify hazards for each task, rate likelihood and severity, add controls until risk is acceptable (method statements / JSAs). Permits to work control high-risk activities: hot work, excavation, working at height, confined spaces, electrical isolation (lockout-tagout).

Safety management and design for safety

Safety management systems (ISO 45001), leading indicators (near-miss reporting, inspections) and lagging indicators (LTIFR), safety culture and leadership. CDM-style regulations require designers to eliminate or reduce risks in their designs and pass on residual risk information.

Formulas

• Risk rating: Risk = Likelihood (1–5) × Severity (1–5)
• LTIFR: LTIFR = LTIs × 1 000 000 / hours worked
• Ladder angle rule: base distance = height / 4 (≈ 75°)
• Heinrich ratio (indicative): 1 major : 29 minor : 300 near misses

Worked example: Safety performance

Given: 3 lost-time injuries; 800 000 hours worked

Find: LTIFR.

• LTIFR = 3 × 10⁶/800 000 = 3.75

Answer: 3.75 per million hours

Worked example: Ladder set-up

Given: Ladder reaching 8 m up a wall

Find: Base distance.

• Base = 8/4 = 2 m (≈ 75°); extend 1 m above landing and secure

Answer: 2 m from the wall

Common mistakes

• Wrong: Relying mainly on PPE. — Right: Apply the hierarchy — eliminate and engineer out hazards first.
• Wrong: Unsupported trenches deeper than 1.2–1.5 m. — Right: Shore, bench or slope excavations and keep spoil back from edges.

Applications

• Site safety planning: Method statements, lift plans, excavation and scaffold designs.
• Design for safety: Designers reduce risks of construction, maintenance and demolition.
• Regulation & certification: ISO 45001, statutory inspections and audits.

Key takeaways

• Falls, excavations, lifting and electricity are the big killers.
• Eliminate → substitute → engineer → administer → PPE.
• Assess risk; use permits for high-risk work.
• Designers and planners shape safety most.

Going further

• Temporary works design: Scaffolds, formwork, shoring and crane bases are engineered structures with checkers.
• Behaviour-based safety: Observation and feedback programmes improve safe behaviours.
• Leading indicators: Near-miss reports and inspections predict and prevent incidents.