A Unified Framework for Safe System Implementation

The Safe System Approach (SSA) is a foundational element of US transportation safety policy, yet its implementation has often remained siloed, reactive, and disconnected from broader systemic change. To advance Vision Zero goals and institutionalize safety across disciplines, we propose a Unified Safe System Implementation Framework for state and local transportation agencies that brings together global best practices in public health, context-sensitive design, and kinetic-energy risk management. The framework addresses three core insights: the centrality of exposure, severity, and likelihood in managing injury risk; the need for context-driven strategies that align with movement and place functions; and the importance of prioritizing interventions based on population impact, survivability, and required user effort. We ground this framework in literature from public health, complete streets, occupational safety, and sustainable transport theory, including the Safe Systems Pyramid, Movement and Place, and Avoid-Shift-Improve models. Our proposed matrix-based structure links SSA elements to context types and intervention tiers, from demand management and speed management to conflict reduction, vehicle technology, and post-crash care. This conceptual, implementation-oriented framework is intended to help practitioners translate Safe System principles into practice, align strategies across departments, and prioritize upstream actions that institutionalize safety. We highlight California’s 2025 Joint Secretary’s Policy on Road Safety, which focuses on institutionalizing upstream, population-level interventions for injury prevention, to illustrate recent efforts to embrace and advance this framework. We conclude with recommendations to refine tool selection, support target-speed setting and management, integrate AI-driven risk assessments, and explore strategies that advance daily safety and emergency response needs.