Passive-Active Safety integration

By Prakash “Krish” Krishnaswamy

THE PATH TO PERSONALIZATION OF AUTOMOTIVE SAFETY

The Automotive industry and its regulators face a uniquely complex safety challenge: a mind-boggling diversity of people, vehicles, behaviors, environments, and combinations thereof. Real-world crashes are stochastic. To function amid this colossal heterogeneity, the industry has historically relied on simplification – classifying occupants into broad percentile categories (5th, 50th, 95th) and reducing real-world crashes to a small set of standardized scenarios such as frontal, side, or offset impacts. These abstractions have enabled remarkable progress, but they are, by necessity, approximations.

Today, that long-standing paradigm stands on the brink of disruption. Advances in sensing, computation, simulation, and systems engineering now make it possible to move beyond coarse averages and toward safety solutions that respond to the individual and the situation. The era of personalized safety is no longer aspirational; it is approaching reality.

The automotive safety story began with Passive Safety – seat belts, airbags, and increasingly sophisticated structural designs guided by biomechanics and

crashworthiness research. Over time, safety practices expanded to include Active Safety, starting with technologies such as anti-lock braking systems, electronic stability control, and later automatic emergency braking, all aimed at preventing or mitigating crashes before they occur.

We are now entering the next chapter: the convergence of Passive and Active safety. No longer independent domains, these approaches are beginning to work in concert – using predictive sensing and real-time intelligence to tailor occupant protection to the person, the posture, and the crash. This Passive-Active safety convergence marks a fundamental shift in how vehicles protect their occupants, and it sets the stage for truly adaptive restraint systems.

THE PERSONALIZATION OF SAFETY

Personalization of Safety offers intriguing new possibilities with the ability of vehicle systems to detect, identify and adapt safety systems to the specific profiles of the occupants and adapt restraint systems accordingly.

Drivers of Adaptive restraint adoption

The “Zero Fatality” vision, driven initially in Sweden, and now by multiple Government bodies, has motivated organizations like Euro NCAP to define their regulatory vision for 2030. The Zero Fatality vision is fueled by the ethical principle that all lives have equal value and EVERY life is worth saving and death/injury is preventable, not inevitable. Euro NCAP Vision 2030 places a high priority on In-cabin monitoring for driver alertness and Child and Pet detection.

Crash avoidance depends on robust sensing and vehicle adaptation to the external environment, while crash management relies on precise sensing and intelligent restraint strategies within the vehicle’s interior.

Euro NCAP places strong emphasis on driver monitoring and plans to expand, by 2026, to full occupant monitoring. This capability will support the detection of driver impairment and facilitate safe transfer of vehicle control in semi-autonomous driving scenarios.

Crucially, driver and occupant monitoring can be used to proactively optimize occupant protection systems—including seat belts, airbags, head restraints, and seat positions/orientation—based on the detected occupant profile. For example, airbag deployment aggressiveness can be tuned in real time during a crash event, adjusting inflator parameters to match occupant size, posture, and seat position. This allows the system to optimize force and timing, reducing injury risk while ensuring effective restraint.

Adaptive restraints

Adaptive restraint systems are a key enabler of personalized safety. The restraint systems are intelligent and account for the occupant’s physical profile and also the seating posture, belt usage, pretensioner and load-limiter states, seatback inclination, and even seat orientation in future autonomous vehicles.

Importantly, these systems can adapt in real time, continuously refining restraint strategies as the crash pulse progresses, rather than relying on a single, pre-determined response.

In Adaptive Seat Belt systems, load limiters and pretensioners play a key role. The pretensioner is activated in pre-crash mode. The load limiter adjusts the force level in real time during the crash pulse and is adapted to the occupant profile.

Adaptive Airbag systems substantially optimize the timing of airbag deployment, inflation energy and venting to manage head and chest G, ride-down, head-to-torso timing and rebound.

For example, the Volvo EX60’s Multi-adaptive safety belt offers a comprehensive adaptive restraint system. It offers safety personalization by profiling the occupant and using AI technology, it automatically selects from eleven different load-limiting profiles that work on real-time basis taking into account such factors as direction, speed, and passenger posture. Further, the vehicle’s Over-The-Air (OTA) updates new real-world scenarios and improves the performance over time.

THE BENEFITS OF SAFETY PERSONALIZATION

The benefits of safety personalization are both significant and increasingly evident in production vehicles. By tailoring restraint and protection strategies to the individual occupant and the specific crash scenario, personalized safety systems offer meaningful improvements over traditional, one-size-fits-all approaches.

First, safety personalization has the potential to substantially reduce injury risk for vulnerable populations, including children and older occupants, who are more susceptible to injuries from aggressive airbag deployment, sub-optimal seating positions, and out-of- position conditions. Occupant classification that accounts for body size, age-related fragility, and posture enables restraint systems to respond more appropriately. Similarly, detection of obesity is becoming increasingly important, particularly in autonomous or highly automated vehicles, where non-ideal seating postures and mass distribution may also influence vehicle dynamics and handling.

Second, adaptive airbags and seat belts can significantly mitigate peak chest loading and head acceleration during a crash. Although the number of frontal impact studies evaluating adaptive restraint systems remains limited, early results are encouraging. Test programs have reported reductions of up to 33% in Head Injury Criterion (HIC), 25% in peak chest acceleration, and 40% in chest compression when compared to conventional restraint strategies.

While these findings are preliminary, they represent important incremental steps toward the industry’s long-term vision of zero fatalities and serious injuries.

THE CHALLENGES FOR SAFETY PERSONALIZATION

Sensing, recognition, and classification technologies are evolving rapidly to support adaptive restraint systems. The question is whether the benefits of this paradigm can be realized and deployed broadly in the near term.

1. Unbounded occupant and crash variability: The combinations of occupant sizes, postures, seat positions, and restraint configurations are virtually Establishing engineering guidelines, regulatory frameworks, and validation procedures for this vast design space using traditional physical testing is impractical. Virtual validation and homologation offer a viable path forward, but their widespread adoption will require extensive standardization of processes, models, and protocols across the global industry and regulatory authorities.
2. Complex injury modeling: Extending protection across a wide range of anatomies demands the development and validation of sophisticated injury models that can accurately predict outcomes across diverse This requires sustained research effort and consensus within the biomechanics and safety engineering communities.
3. Litigation and liability considerations: As with most advances in automotive safety, personalized systems introduce scenarios where outcomes are difficult to predict or explain post-crash. Unresolved or ambiguous injury or fatality situations could increase legal exposure and pose costly litigation risks.

Addressing these challenges will require close collaboration across manufacturers, suppliers, regulators, and the research community. Only through coordinated efforts can the promise of safety personalization be realized at scale.

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