Hazard Analysis
Activity
Topic overview
Quick facts
Hazard analysis is a family of techniques, not a single method, and the members have distinct jobs at distinct lifecycle moments.
At concept, a preliminary hazard analysis (PHA) casts a wide net from limited design detail: functions, energy sources, operating situations, and historical incident data generate a first hazard inventory that shapes architecture while change is cheap.
The domain-specific concept-phase forms are the for automotive, the risk assessment for machinery, and the system hazard analysis feeding the hazard log in rail practice, each combining hazard identification with risk estimation to set integrity targets.
As design matures, causal analyses take over: fault tree analysis works top-down from each hazardous event to the combinations of failures and conditions that could produce it, exposing single points of failure and common-cause weaknesses, while works bottom-up from components to effects, ensuring no single failure mode was overlooked.
The two are complementary by construction, cannot see combinations, FTA cannot see failure modes the analyst did not include, and standards expect both perspectives at higher integrity levels.
Specialized forms fill gaps: interface and integration analyses, operating and support hazard analysis for maintenance and human tasks, and SOTIF-style triggering-condition analysis where hazards arise without any fault.
The thread tying the family together is the hazard log (or hazard tracking record): every identified hazard enters it with its risk assessment, traces to the requirements and measures that control it, and remains open until evidence closes it. The log is typically the first document an assessor or authority reads and the last one closed before acceptance.
Why Hazard Analysis matters
Every integrity target, safety requirement, and test campaign in a safety program traces back to a line of hazard analysis, so its quality bounds the quality of everything downstream: a missed hazard is a missing requirement that no amount of excellent verification will catch, and analysis done late documents a design instead of shaping one.
For product leaders the staging is the point to manage: a rough PHA in week one influences architecture nearly for free, while the same insight surfacing in assessment costs a redesign, making early, admittedly imperfect analysis one of the best investments in the program.
How Hazard Analysis is applied
Hazard analysis activity
Run the family in stages: a PHA at concept from functions, energy, use cases, and field history; the domain's concept-phase risk assessment (, assessment, or system hazard analysis) to set integrity targets; FTA and during architecture and detailed design to validate the design against those targets; and operational and maintenance hazard analysis before deployment.
Facilitation is cross-functional, safety engineering structures the sessions, but the hazards live in the heads of designers, operators, and service technicians.
Assessors evaluate coverage arguments (how the team knows the hazard space was searched systematically rather than brainstormed), consistency between the analyses and the as-built design, and hazard log closure with evidence rather than assertion.
Hazard Analysis pitfalls to avoid
Standards related to Hazard Analysis
Hazard Analysis is defined and governed by ISO 12100 - the foundational machinery safety standard establishing risk assessment methodology and the hierarchy of risk reduction.
ISO 26262 sets the requirements that Hazard Analysis work has to satisfy: automotive functional safety standard defining asil levels and the automotive safety lifecycle.
EN 50126 sets the requirements that Hazard Analysis work has to satisfy: specification and demonstration of reliability, availability, maintainability and safety for railway applications.
Common hazard analysis methods
| Method | Style | Typical domain |
|---|---|---|
| PHA | Early, checklist-driven | Rail, aerospace, general |
| HAZOP | Guideword deviations | Process plants |
| HARA | S/E/C rating to ASIL | Automotive |
| STPA | Control-structure, unsafe control actions | Complex software-intensive systems |
| FHA | Function loss/malfunction | Aerospace |
Hazard Analysis by industry
Hazard Analysis shapes how industrial machinery teams argue safety - fixed and mobile machinery, packaging lines, and manufacturing equipment.
In rail & transit, Hazard Analysis comes up in nearly every certification conversation: freight and passenger rail signaling, train control, and transit systems.
Hazard Analysis shapes how autonomous systems teams argue safety - autonomous mobile equipment, off-highway autonomy, and driverless platforms.
Ask our team about Hazard Analysis
Ben TwomblyFounder & CEOLeads CSA's functional-safety, certification, and engineering programs for safety-critical products and organizations. His assessor-side background informs practical programs that connect standards, engineering work, and credible evidence.
Jeff Twombly, PEExecutive, Rail SafetyProvides executive and technical leadership for rail-safety programs, assessments, and complex transit-system work. His experience spans safety assurance, transportation-safety leadership, signaling, and independent review.
Tom CyrPrincipal Safety Engineer, IFSPSupports industrial and rail functional-safety programs with safety analysis, requirements, lifecycle planning, and certification-readiness guidance.Hazard Analysis: related terms
How each connects to Hazard Analysis:
Programs that deal with Hazard Analysis almost always involve Risk Assessment in the same phase.
Fault Tree Analysis appears in the same lifecycle work as Hazard Analysis and is usually produced or reviewed alongside it.
ISO 26262 connects the two: Hazard Analysis and ASIL are assessed against the same lifecycle.
ISO 12100 connects the two: Hazard Analysis and Hierarchy of Risk Reduction are assessed against the same lifecycle.
ISO 26262 connects the two: Hazard Analysis and FMEDA are assessed against the same lifecycle.
ISA is governed by EN 50126 as well, which is why the two show up together in audits.
Both Hazard Analysis and CENELEC Rail Standards sit under EN 50126, so evidence for one usually references the other.
ATO is governed by EN 50126 as well, which is why the two show up together in audits.
Both Hazard Analysis and CE Marking sit under ISO 12100, so evidence for one usually references the other.