CHAPTER 1

Background of the Safe System

Since the introduction of the private automobile in the United States, traffic safety has undergone at least four distinct yet interrelated paradigms. These paradigms shaped how travel speed was perceived (e.g., as inherently dangerous or safe with the right road or vehicle designs), which parties were considered responsible or innocent in the event of a collision, the role of road and vehicle design in safety, and the inevitability or preventability of serious crashes. According to Norton (2015), the concept of traffic safety emerged in the early 1900s with the introduction of the motor vehicle and a focus on the safety of child pedestrians and the role of vehicle speed in safety outcomes. This period, which ushered in a Safety First paradigm, coincided with the establishment of the National Safety Council (NSC) in 1913 (NSC 2024b). In the 1920s and ’30s, Safety First campaigning gave way to a Control paradigm, which empowered a growing class of professional traffic engineers [e.g., ITE, formed in 1930; (ITE 2024)] and law enforcement who provided expert engineering (highway-focused), education, and enforcement to prevent serious crashes. The Control paradigm was later superseded by a Crashworthiness paradigm in the 1960s and ’70s, which maintained a focus on the safety of vehicles [e.g., Ralph Nader published his book Unsafe at Any Speed in 1965; Nader (1965)]. Traffic deaths exceeded 40,000 for the first time in 1962, then 50,000 in 1966 (NSC 2024a). During the Crashworthiness paradigm, advocates and organizations called for improved vehicle design to protect vehicle occupants (e.g., seatbelts became ubiquitous, and airbags were introduced in the 1970s). The 1980s ushered in a Responsibility paradigm, which centered safety discussion on the role of responsible drivers and appears to be the prevailing paradigm of today. Alternatively, the Safe System, with its emphasis on proactively addressing safety, instituting system redundancies, and managing travel speeds, might represent a new paradigm, one in which the United States has witnessed growing interest and investment.

Indeed, for the past decade local, state, and federal commitment to advancing the safety of the U.S. transportation system and realizing a future without serious and fatal injury has been increasing (Shi et al. 2023; Evenson et al. 2023). Organizations and agencies have adapted road safety philosophies from abroad to propose a Safe System approach (FHWA 2019a). Most typically, a Safe System is thought to be shaped by pragmatic principles (e.g., redundancy is crucial, safety is proactive) and ethical ones (e.g., death and serious injury are unacceptable) and comprises the following safety elements: safe road users, safe vehicles, safe speeds, safe roads, post-crash care (Vision Zero Network 2023; FHWA 2019a).

Today, in the transportation industry, the term “safety” typically refers to the probability of harm while traveling (e.g., a higher level of safety indicates a lower level of harm). Another general definition presents it as an absolute value, meaning freedom from harm or not involving any risk of severe injury (Sakashita, Job, and Belin 2022).

These guidelines were developed with the understanding that transitioning to a Safe System would initially favor probabilistic definitions of safety given the current state of the practice

• Safety is proactive. Proactive methodologies and tools should be used to identify and address safety issues in the transportation system, rather than waiting for crashes to occur and reacting afterward.

  This principle indicates any death or serious injury by the transportation system should trigger a response aimed at understanding how to systematically prevent its repetition, followed by whatever investment of resources and implementation of changes are required to make this happen. Whenever streets or roads are reconstructed, layouts should be modified to reflect Safe System best practices. Safety features such as neighborhood traffic calming should be implemented proactively, not only as a response to collision hotspots or neighbors’ complaints. Continual study of designs should lead to improvements in design standards, as should research from other parties such as universities.

• 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 roadways (WHO 2023).
• Redundancy is crucial. Reducing risks requires all parts of the transportation safety system to be strengthened, so if one part fails, the other parts still protect people. This principle focuses on the elements of the system that provide reliable protection for road users when other elements of the system fail, which requires designing robust backup systems, such as cable-wire barriers to catch drivers who leave the road when their vehicle’s lane-keeping technology fails (Alluri et al. 2016).

Applying Safe System Principles

The following sections outline applications of the Safe System principles in planning, design, operations, and safety practices that collectively have the potential to transition the United States toward a truly Safe System (Figure 1).

Following is an example of a Safe System principle and corresponding strategy and practices:

Principle: Humans are vulnerable.

Strategy: Design around human tolerances to crash forces.

Practices: Installing permanent barrier-protected bike lanes on arterial roads; Installing cable barriers on the edges and in the medians of rural roads.

Safe System elements (e.g., safe roads, safe speeds, safe road users) are the results of the activation and advancement of Safe System principles, strategies, and practices.

Safe System Pillars (Elements/Outcomes)

Safe vehicles ensure drivers will not crash into people or objects with human-intolerable force by providing intelligent speed assistance depending on the operating context. They are designed to enhance visibility of vulnerable road users with direct vision, lane keeping, and automated emergency braking, among other safety features.

Safe speeds are aligned with known human tolerances to closing/impact speed forces, varying speeds by the road and land-use contexts, as well as road-user mix.

Safe roads are self-explaining and enforcing, automatically cueing drivers to engage in context-appropriate, desired behaviors, and they are designed with energy-absorbing protections (e.g., breakaway poles, see Vardaki, Papadimitriou, and Kopelias 2014). They have sufficient task saturation to keep drivers alert, but not overwhelmed (Calvert and van Arem 2020). Furthermore, they are based on likely interactions of vehicles and users of different speeds, directions, and masses (Johansson 2009).

Post-crash care is well resourced, equipped with crash predictive capabilities, inclusive of Next Generation 911 (NG911) functionality, better able to access level 1 and 2 trauma centers across the country, and part of safety planning to improve crash scene management and prevent secondary crashes and injuries (Liu 2022).

Safe road users are the desired result of a Safe System. They value safety, endorse safety regulations, understand and appreciate the reasons for safety policies and investments, and elect policymakers partly on evident safety-oriented values and interests.

1.2 Organizational Principles

A Safe System provides professionals with clear principles from which to operate. “Death and serious injury is unacceptable” is the first and ethical principle of the Safe System. It is followed by the principles about the psychological and physiological realities of human road users, “humans make mistakes” and “humans are vulnerable.” Next are the practical principles “safety is proactive” and “redundancy is crucial.” The final principle, “responsibility is shared,” is interpreted for the purposes of this guide as an interorganizational principle and framed as “system operator responsibility” (see the “System Operator Responsibility” section for more information). To activate the Safe System principles, the following guidelines offer organizational principles around organizational change management, system operator responsibility, learning and innovating, communications and messaging, and participation in decision-making.

Change Management

The first organizational principle is rooted in the concept and practice of change management. This practice starts with authentic leadership and the central notion that change is necessary and possible.

• Change leaders begin change management by communicating to managers and employees the need and urgency for change, articulating why the organization cannot stay in its current state and that a better place from which to operate exists (Luecke 2003).
• Leaders and managers, in partnership, invite groups within the organization to define and commit to realizing expressed change goals. They jointly identify existing problems with the organization’s approach to road safety and develop solutions (Al-Haddad and Kotnour 2015).
• Next, leaders encourage the group to focus on realizing the change goals and appropriately engaging all the people who own the change in carrying out the necessary work to realize

• change. More explicitly, leaders create space for groups to share their perspectives on the status quo and where they would like to end up, find belonging with those who share common cause, and make clearer everyone’s value in the change-making process (Errida and Lotfi 2021).
• Leaders also manage the space for the group by establishing and enforcing (1) team-working norms (e.g., trust and communication norms), (2) quality improvement tools for testing out new safety policies and practices via demonstration projects, and (3) task-management tools for tracking progress over time and sustaining momentum (Phillips and Klein 2023).

System Operator Responsibility

Under this second organizational principle, professionals involved in designing, operating, and maintaining roads and vehicles, as well as those providing injury surveillance and coordinating post-crash care and trauma response, are collectively responsible for maximizing the safety of vehicle and road designs and operations (Shi et al. 2023). In short, system operators should be held accountable for delivering the road-using public a Safe System (Soames Job, Truong, and Sakashita 2022).

Learning and Innovating

As social and political norms shift and technologies become more commonplace, Safe System professionals and researchers will need to remain nimble in their work. They will need to examine the questions they are asking and expand them; for example, “does this countermeasure work?” becomes “does this countermeasure work, why does it work, and in what contexts does it work?” Adopting a habit of continual learning and innovating supports the complex system within which society operates (Adams et al. 2016). It would benefit road safety professionals and researchers to develop a holistic understanding of their community’s road trauma patterns and injury contributors, as well as timely feedback on the safety risks and performance of implemented countermeasures. Iterating, learning, and innovating in this way can help safety analysts account for demographic shifts, and simultaneously implemented policies, in their safety impact assessment, something deterministic CMFs cannot do (Noland 2013).

Communications and Messaging

Avoid individualism. Placing blame on victims of road trauma harms the victims and those close to the victims and fails to inspire calls for altering the system in community-benefiting ways. Instead, whenever possible, reference the context in which road users operate and in which serious crashes occur.

Frame the Safe System as a viable solution to road trauma. Though it is common to learn many people die on U.S. roads each year, such bad news, when presented without information on solutions, can incite cynicism rather than motivation to improve the situation. Instead, introduce solutions to road trauma early and often and in ways that remind policymakers and the public how serious traffic injury and death can be prevented. Following are a few tips (adapted from Frameworks Institute 2022):

• Help people visualize how one or more safety interventions work [e.g., “Replacing traffic lights with roundabouts can reduce deadly traffic injuries by 90% by lowering the speed of vehicles entering the intersection and changing the angles at which any crashes may occur, avoiding deadly side-impacts” (Michael et al. 2023)].
• Emphasize solutions that involve different people coming together to reduce road trauma (e.g., “Law enforcement officers informed the city’s transportation engineers that pedestrians were often crossing between intersections in places without marked crosswalks and being struck. After observing conditions, the planning and engineering teams designed and installed a raised crossing in a location where most pedestrians were already crossing, thereby greatly reducing midblock pedestrian crashes”).

• Talk about preventing road trauma as doable and within reach (e.g., “By lowering our posted speed limits, adding road elements to encourage slower speeds, and providing more physical barriers between people driving cars and those riding bicycles, we are seeing a major drop in people being injured on our roads. We look forward to making many more safety improvements in the months and years ahead”).
• After a crash, reference the human toll of road trauma (e.g., “This and every death affects the victim’s family, friends, and broader community”).
• Place crashes in time- and place-based context (e.g., “This is the fifth deadly run-off-road crash on Old Greensboro Rd in the past few years”).
• Note how road injuries are preventable through proven means and how improving safety benefits everyone [e.g., “Road improvements such as rumble strips can prevent run-off-road crashes, which can result in disabling injuries. All of us who use rural roads would benefit from a backup system for when something goes wrong” (Michael et al. 2023)].

Participation in Decision-Making

Safe transportation access starts with representation in decision-making (Karner and Marcantonio 2018; McCullough and van Stokkum 2021). If a safe transportation system is to be built, there should be broad representation of community members in decision-making (Bello-Bravo, Medendorp, and Pittendrigh 2022).

Participation in decision-making can ensure that what is counted as useful data, information, or knowledge in the realm of traffic safety includes the first-person perspectives of people who have lived experience—also recognized as “lived expertise”—contending with often unsafe and unreliable transportation systems (Lowe, Barajas, and Coren 2023). Safety analysts should not rely solely on police-documented crash data to discern injury hot spots or to allocate scarce resources. Instead, analysts should also aim to incorporate community members’ perspectives into their problem identification and countermeasure selection procedures.

The ability to participate in decision-making and offer one’s lived expertise to addressing safety problems holds promise for increasing community members’ trust in the legal system (Bottoms and Tankebe 2020) and improving the distribution of high-quality infrastructure and transportation services (Pereira, Schwanen, and Banister 2017).

1.3 Safe System Strategies and Practices

Bridging Safe System Principles, Strategies, and Practices

In the following chapters, this guide proposes several domain-specific Safe System strategies for professionals to consider adopting, adapting, and implementing in their work. These Safe System strategies provide a conceptual and practical bridge between Safe System principles and practices, being neither lofty nor “on-the-ground.” Instead, these strategies offer longer-term orientations toward key safety practices.

An example design strategy is to base design on known human tolerances to crash forces. An example policy strategy is to advance adaptive safety policies rather than inflexible ones. An example planning strategy is to replace forecasting with backcasting. Each of these strategies channels one or more Safe System principles (e.g., humans are vulnerable, safety is proactive, and redundancy is crucial) and brings the principles closer to actual safety practice.

A Safe System practice, on the other hand, is something that is usually or regularly done, often as a habit, tradition, or custom. In this guide, a safety practice can also mean an intervention or program that (1) significantly enhances understanding of contributing factors or outcomes