By Megan Link
Traditional transportation safety frameworks like the three Es (Engineering, Enforcement, and Education) are impeding strategies that will reduce traffic deaths and improve overall population health, says a new study. The study introduces the Safe Systems Pyramid, a framing of the Safe Systems approach designed to prioritize policies and programs that incorporate health principles into transportation decision making. By combining public health efforts with transportation strategies and practices, the authors propose an alternative approach that moves away from identifying crash outcomes and toward addressing the causes of safety crises.
The three Es, introduced in the 1920s, were designed to reduce traffic-related deaths by balancing Engineering, Enforcement, and Education. A century later the three Es are still informing transportation safety programs at agencies like the NHTSA while pedestrian and traffic deaths continue to rise. To counter this, the authors propose the Safe Systems Pyramid as the paradigm shift transportation professionals should prioritize to integrate public health principles, maximize population health impacts, and plan intervention points to reduce traffic and pedestrian deaths. The Safe Systems Pyramid combines Vision Zero and Safe Systems approaches and is modeled after the Health Impact Pyramid.
The Safe Systems framework focuses on maximizing population health impacts while minimizing individual efforts through a combination of approaches and tiers. The authors note:
“The pyramid structure is intended to help engineers and other road safety practitioners understand the population health impact of various interventions. No single strategy can be effective alone, and transportation professionals must make use of interventions at each level of the pyramid given their jurisdictions…This framework argues that such a siloed approach to transportation safety will not improve safety outcomes; viewing crashes as a public health problem requires those working in transportation safety to consider and attempt to improve the underlying social context in which these crashes take place.”
Understanding each tier of the framework can form the context for transportation professionals to prioritize interventions based on current resources and potential impact for the population.
Socioeconomic Factors: The bottom tier determines the context for health and safety outcomes. Socioeconomic factors influence travel behaviors and risk of injury. Potential intervention points include zoning policies like affordable housing near transit and reform that reduces vehicle miles traveled. This intervention requires a large upfront cost and political will—often hard to obtain in many contexts.
Built environment: The built environment combines land use and a person’s interactions with the environment as they travel, directly influencing driving patterns, risk of high-speed crashes, and overall travel modes. Intervention points can include roundabouts, speed bumps, and design guidance focused on safety more than capacity. Intervention points in this tier can be very influential without targeting individual behavior.
Latent safety measures: Latent safety measures are design features of cars and signals that can decrease the level of health risk if there is a high percentage of individual compliance. Examples include signal timing, air bags, and vehicle standards.
Active measures: Active measures are most effective at the individual level and their benefits directly involve individuals. Stop signals, seat belts, and helmets are individual actions that can greatly increase safety.
Education: Education, although typically the least controversial, is the most individualized of the tiers and the least universal. Strategies like driver education programs and other programs promoting safety can be effective but are dependent on each individual’s behavior.
Our current transportation system poses a public health problem, exacerbated by outdated approaches to safety planning and prioritization. Shifting the way engineers, planners, and policymakers think, by adopting a Safe Systems framework, may foster collaboration, new strategies, and an overall emphasis on the factors that will have the largest impact on safety and public health.