HARA Excellence: What Makes a World-Class Hazard Analysis

When Toyota recalled millions of vehicles in 2009 for unintended acceleration, the automotive industry learned a harsh lesson. Inadequate hazard analysis and risk assessment and safety analysis in general, can cost lives, reputation, and billions of dollars. At the heart of preventing such disasters lies HARA: Hazard Analysis and Risk Assessment. This systematic process is the cornerstone of ISO 26262 that separates world-class automotive safety programs from those leaving public trust to chance.

But what transforms a basic HARA from a compliance checkbox into a powerful safety engineering tool? The answer lies in understanding not just what to analyze, but how to analyze it with precision, depth, and practical engineering wisdom.

What Makes HARA the Foundation of Automotive Safety

HARA serves as the critical bridge between abstract safety concepts and concrete engineering requirements. The process answers three fundamental questions. What can go wrong at the vehicle level? How severe could the outcome be? What level of safety rigor is required to prevent it?

The process systematically examines every operational situation where a system malfunction could cause harm, then classifies each hazardous event using a three-dimensional risk assessment framework:

• Severity (S): The estimate of potential harm to individuals in a specific operational situation. It ranges from no injuries (S0) to light and moderate injuries (S1), severe injuries where survival is probable (S2), and life-threatening or fatal injuries (S3).
• Exposure (E): The probability of being in an operational situation that can be hazardous if coincident with the failure mode. It ranges from incredible (E0) to high probability (E4).
• Controllability (C): The ability of the driver or other persons at risk to avoid a specified harm through timely reactions. It scales from controllable in general (C0) to difficult to control or uncontrollable (C3).

These ratings combine to determine your ASIL (Automotive Safety Integrity Level), which dictates the rigor of safety activities required throughout your development process.

Remember: ASIL is not a direct mathematical probability of failure. It is a discrete classification system that determines the necessary depth of safety measures, architectural redundancies, and process rigor needed to achieve the absence of unreasonable risk.

Characteristics of Excellent HARA: Beyond Basic Compliance

Outstanding HARA work shares several distinguishing characteristics that separate industry-leading safety teams from those merely checking boxes.

Situation-Specific Precision

Generic safety goals like "prevent unintended braking" provide little actionable guidance. Excellent HARA creates situation-specific safety goals that directly translate into testable safety requirements. Instead of vague statements, precise scenarios are defined. A better example is: "Prevent false positive braking exceeding 3m/s² at vehicle speeds above 80km/h on highways."

This approach recognizes that the identical system fault can have dramatically different consequences depending on the operational context. False braking during highway merging demands a different risk assessment and validation strategy than false braking during low-speed parking maneuvers.

Evidence-Based Classifications

World-class HARA teams do not guess at Severity, Exposure, and Controllability ratings. They rely on objective data. Severity classifications reference medical data from the Abbreviated Injury Scale (AIS) and established crash databases. Exposure ratings draw from real-world driving data, fleet statistics, and operational design domains. Controllability assessments incorporate human factors research, naturalistic driving studies, and simulator data.

For example, when assessing controllability for an Electric Power Steering (EPS) system, leading teams conduct simulator studies with naive drivers to determine realistic human reaction times, rather than making arbitrary engineering assumptions about driver capability.

Comprehensive Scenario Coverage

Excellent HARA systematically explores edge cases, environmental factors, and human behavior variations rather than stopping at obvious failure modes. Crucial scenarios often missed include:

• System degradation in adverse weather conditions or low-traction surfaces
• Interactions with other vehicle control systems during fault conditions
• Driver behavior variations, including elderly, impaired, or distracted drivers
• Infrastructure variations such as poor road quality, missing signage, or glare

HARA Strategies for Different System Types

The HARA approach must adapt to the unique characteristics and operational domains of different automotive systems.

Advanced Driver Assistance Systems (ADAS)

ADAS functions operate in complex, dynamic environments with significant uncertainty. The hazard analysis must account for sensor limitations, environmental degradation, and the delicate balance between system safety and functional availability.

For ADAS functions, safety engineers must pay special attention to:

• False positive interventions that could initiate secondary accidents
• Degraded performance in adverse weather or unusual road geometry
• Driver adaptation and the potential for overreliance on automated functions
• The precise transfer of control between the system and the driver

Level 3 Automation Complexity

Level 3 automated driving systems introduce unprecedented HARA complexity because the fallback-ready user is permitted to perform secondary tasks. The analysis must consider Take-Over Request (ToR) timeframes, Minimum Risk Maneuvers (MRM), and the reality that drivers will be out of the control loop when a fault occurs.

These systems frequently result in ASIL D classifications for critical vehicle control functions. This is due to high exposure (E4 for continuous highway operation) combined with challenging controllability (C3), as the driver cannot be expected to instantly mitigate sudden lateral or longitudinal control faults.

Practical HARA Excellence Checklist

Use this structured framework to evaluate and improve your HARA quality:

CategoryQuality CriteriaScope and CompletenessAll operational situations and vehicle-level hazards are identified. Edge cases, environmental variations, and system interactions are fully documented.Classification RigorSeverity references AIS data. Exposure uses verifiable fleet or traffic data. Controllability is backed by human factors evidence. All rationales are explicitly cited.Safety Goal QualityGoals are situation-specific, verifiable, and assigned the correct ASIL. There is a clear, traceable derivation path from the hazard to the top-level safety requirements. This systematic approach transforms HARA from administrative overhead into a powerful engineering tool that guides every subsequent safety decision.

Beyond Compliance: HARA as a Strategic Engineering Tool

The most successful automotive safety teams view HARA not as a compliance burden, but as a strategic tool that shapes product architecture, validates design decisions, and communicates risk effectively across the organization.

When executed rigorously, HARA becomes a guiding compass. It directs resource allocation, hardware redundancies, software monitoring strategies, and validation priorities throughout the entire safety lifecycle. It transforms abstract safety objectives into concrete engineering actions that directly impact product quality.

The complexity of the automotive industry continues to grow. Electrification, automated driving, and advanced connectivity introduce new failure modes and interaction effects that traditional approaches struggle to address. Mastering advanced HARA methodologies is about building the engineering capability to safely navigate this evolving landscape, ensuring the absence of unreasonable risk in every vehicle produced.

Ready to elevate your HARA skills beyond basic compliance? Dive deeper with our comprehensive Hazard Analysis and Risk Assessment concept on the ISO 26262 Academy platform. Discover advanced techniques like situation-specific safety goals, quantitative Fault Tolerant Time Interval (FTTI) derivation methods, and industry case studies that transform theoretical knowledge into practical expertise. Master the techniques that separate world-class safety engineers from the rest.