We’ve all seen it: the exhaustive safety analysis delivered to engineering teams, long after critical design decisions have been made. Implementation of it, leads to redesigns of the system. So engineers fight with safety requirements, to neglect them. It’s a classic case of too little, and too late. While well intentioned, this traditional approach to safety, focused on component reliability and redundancy, is fundamentally flawed in today’s complex, software-driven world. It’s time Shift the Paradigm to STAMP (and STPA of course).
For too long, safety engineering has been a parallel track to system design, not an integral part. The result? Expensive, over-engineered systems that may not even address the most critical hazards. We’re left with a false sense of security, relying on redundant components and safety margins. They primarily tackle simple hardware failures, while completely missing the bigger picture: Complex interactions between components and the people who operate them.
This is where the Systems-Theoretic Accident Model and Processes (STAMP) comes in. It’s offering a more holistic and effective framework for safety. Developed by Dr. Nancy Leveson, a leading expert in system safety, STAMP views systems as a dynamic process. STAMP goers above and beyond of a approach where system is static collection of parts.
Imagine a finely tuned ecosystem, where all control loops constantly work to maintain a state of equilibrium. This is the essence of a safe system according to STAMP. This is the way to ensure safety.
The Dynamic Dance of Safety
Think of a complex system, like a modern autonomous airplane. It’s not just a collection of hardware and software. It’s a living entity, constantly adapting to its environment and internal changes. STAMP recognizes this dynamic. It forces us, engineers to move beyond simply asking “What if this component fails?” to a more profound question: “What are the unsafe interactions that could emerge from the system’s normal operations?”.
This is a crucial difference. Traditional methods often focus on preventing component failures. This methods have been really good, for the times they have been developed. In 21st century, where systems are more and more complex, we urgently need a new approach. In today’s reality, accidents in complex systems often arise from flawed interactions between perfectly functioning components. Redundancy and over-design, the go-to solutions in the old paradigm. All this can even increase complexity and creating unforeseen dependencies. Every dependency is next potential unsafe control action.
Mismatched Mental Models – Shift the paradigm to STAMP
STAMP brings a critical aspect to the forefront: the significance of mental models. These are the internal pictures that developers, engineers, and operators have of a system and its behavior. A programmer’s understanding of a software’s logic might not perfectly align with an engineer’s own model. The engineer’s model is of the physical system that the software controls. This seemingly small discrepancy can then lead to catastrophic software requirement errors.
The complexity multiplies together with amount controllers are involved. These controllers can be both human and automated. Each controller operates based on its own unique process model. If these individual models are not consistent with each other, the risk of unsafe control actions skyrockets. The worst place to have is a grey zone, where no controller has a clear ownership of a system. It is like having multiple captains trying to steer the same ship. Each one is using a different map. In such a situation, chaos is inevitable.
Early Intervention: The Key to Effective Safety
One of the most powerful tenets of the STAMP approach is the emphasis on integrating safety analysis from the earliest stages of concept development. Critical decisions that impact the safety of the completed system are made long before the traditional safety engineers even get to their analysis. (FMEA is usually a last step of a system engineering, not a first one).
By the time the hazard analysis is complete, the fundamental design is often set in stone. The safety team is then left with the unenviable task of “patching” the design with add-ons and workarounds, rather than building safety in from the ground up. More complex system is, the more difficult patchwork have to be done. Costs of re-engineering are much higher than original engineering costs!
STAMP, and its practical application through System-Theoretic Process Analysis (STPA), provides engineers with a powerful tool to proactively identify potential hazards and unsafe control actions early in the design process. It doesn’t just label a function as “safety-critical”; it provides a deep understanding of why it’s critical and what specific unsafe outcomes could arise. It also provides a performance criteria, or help to understand system boundaries.
Armed with this knowledge, engineers can make informed decisions, designing systems that are safer, more efficient, and less costly to build and maintain. Instead of blindly adding redundancy, they can focus on designing control structures that prevent hazardous states from ever occurring. Every goal can be included in the analysis: Mission, Safety, Costs, Maintenance, (You name it). With equal rate, they can be weight during the STPA process, and results can satisfy everyone.
Moving Forward: A Call for a New Way of Thinking – Shift the paradigm to STAMP
The message is clear: our reliance on outdated safety analysis methods is a liability to society. We cannot longer afford it. In an era of increasing complexity and software dependency, we need a more holistic approach. STAMP provides that framework. By embracing its principles of dynamic equilibrium, feedback control, and the critical importance of aligned mental models, we can move from a reactive, component-focused approach to a proactive, system-centric one.
It’s time to stop treating safety as an afterthought and start integrating it into the very DNA of our systems. The safety of our systems, and the people who depend on them, hangs in the balance. Don’t pay the Boeing price. Do this wise! If You would like introduce STAMP and STPA to Your organisation, check this article and feel free to contact us!
