The Safe Systems Pyramid: A new framework for traffic safety

Civil engineers play an outsize role in shaping the built environment, which plays an outsize role in health, especially in transportation safety. While there is growing interest in integrating public health and transportation engineering and planning to improve safety outcomes, existing efforts fall short. We review prior efforts to integrate public health into transportation safety, and frameworks from injury prevention and control and risk management. Based on the Hierarchy of Controls and the Health Impact Pyramid, we present a framework for prioritizing policies and interventions, known as the Safe Systems Pyramid, that contains five ascending levels – Socioeconomic Factors, Built Environment, Latent Safety Measures, Active Measures, and Education. The levels of the framework prioritize increased population health impact and decreased individual effort. Frameworks like “The 3 E’s” emphasize collaboration rather than a change in thinking and action among transportation safety professionals, and do not prioritize specific actions. We argue that Vision Zero and other “Safe Systems” prioritize implementation of policies, programs, and infrastructure to increase population health impact by considering the individual effort necessary to obtain a protective effect. This framework is designed to shift the thinking of engineers, planners, and policy makers that shape the transportation system. We conclude this work by applying the Safe Systems Pyramid to a hypothetical Vision Zero program, highlighting how the framework can be used to prioritize efforts using a Safe Systems approach.