Applying the Safe System Approach to Transportation Planning, Design, and Operations (2025)
Chapter: Safe System Principles and Pillars (Elements/Outcomes)
Safe System Principles and Pillars (Elements/Outcomes)
Safe System Principles
Death/Serious Injury is Unacceptable.
This is the moral goal of Vision Zero. There should be no other desired end state than to realize a future without death and serious injury on our roads. This premise requires that all transportation plans and projects be organized around preventing serious road trauma. It follows that this principle obstructs efforts to compromise road user safety in any way (e.g., adding roadway capacity without substantive safety protections). As Dumbaugh et al. (2019) have observed, the goal of building a Safe System is distinct from traditional safety planning with its moral imperative to ensure substantive safety, representing a philosophically and ethically divergent stance, especially compared to cost-benefit frameworks, “which reduce traffic considerations to trade-offs among project costs, high-speed mobility, and road user safety” (p. 61).
Humans Make Mistakes.
Slips (errors of execution of intentions), lapses (errors of behavioral memory storage), and mistakes (errors of planning) are endemic to the human population (Allahyari et al., 2008; Reason et al., 1990). Education and behavior modification programs need to take these natural human proclivities into account when designing behavioral interventions [e.g., graduated driver licensing (GDL) works because novice drivers learn by doing—by driving under increasingly more complex conditions over time (Foss, 2007)]. Knowledge of human fallibility necessitates the design and operation of a system that accommodates inevitable human error.
Humans are Vulnerable.
All users of the road network—especially vulnerable road users, and even those who deliberately take risks or travel recklessly—must never be exposed to human-intolerable energy forces. Job and colleagues (2022) acknowledge the challenge of realizing a truly Safe System yet provide insight into how this can be achieved: integrated roadway and vehicle features that comply with Safe System speed limits, are effective, reliable, and maintained, as well as capable of preventing serious road trauma without reliance on safe road user behavior or compliance with laws.
Safety is Proactive.
As with the first principle (death/serious injury is unacceptable), the corporal safety of road users provides the foundation for all planning, design, operations, and maintenance decisions. Systemic, risk-based safety analyses (e.g., Gooch et al., 2022; Charman, 2018) are consistent with this principle, and provide guidance to agencies on where to allocate scarce resources (Gross and Harmon, 2019).
Responsibility is Shared.
Preventing serious and fatal road injury is possible and requires involvement from government at all levels, health and education sectors, private industries, and civic organizations. All are vital to preventing fatalities and serious injuries on our roadways through funding, implementing, and evaluating effective safety policies, strategies, and practices (World Health Organization, 2023).
Redundancy is Crucial.
The focus on this principle must be on those elements of the system that provide reliable protection for road users when other elements of the system fail. This requires the planning and installation of robust backup systems, such as edge line wire rope barriers that catch drivers who leave the road when their vehicle’s lane-keeping technology fails (Alluri et al., 2016).
Taken together, the principles of a truly Safe System produce the Safe System pillars, elements, or outcomes. Each of the following statements provide descriptions of ideal end states within each of the Safe System elements.
