March 27, 2023 BY Tiffany Smithin News

Fundamentals of the Safe System Approach

Advancing Vision Zero, Shifting the Paradigm for Safe Mobility

The quest for improving roadway safety in the U.S. is a challenge that demands a major collective effort beyond mere dedication, hard work or even more money. And it will take more than declaring commitments to Vision Zero. It will take a real change to the status quo.

This is because despite dedicated road safety professionals, advocacy groups, significant money and Vision Zero pledges, the U.S. still has one of the highest traffic fatality rates in the industrialized world – double the rate in Canada and quadruple that in Europe. In fact, in 2021 drivers struck and killed more people walking in a single year in the U.S. than anytime in the past four decades, while fatal pedestrian crashes have decreased in similar nations.

Not to mention, traffic crashes are the leading cause of death for kids in the U.S. (ages 12 and younger), and they disproportionately impact people who identify as Black, American Indian, and Pacific Islander

However, it doesn't have to be this way. Other nations have made changes that have resulted in significantly safer mobility. What does the U.S. need to do to turn the tide on our preventable roadway safety crisis?

Based on experiences and data-driven analysis, real progress will take a fundamental shift in how we view the problem of roadway safety and which strategies we employ to make change. This includes evolving from the traditional roadway safety approach to a Safe System approach

>> We talked to Vision Zero leaders from Tacoma, WA; Philadelphia; and Denver’s Regional Council of Governments (DRCOG, a regional MPO) about their experiences and lessons learned in developing Vision Zero Action Plans built on a solid Safe System foundation. Check out our recap and the 1-hour conversation.

Word cloud responses from participants when asked what came to mind when they think about the Safe System approach. From a February 2021 discussion, “Pivoting to the Safe Systems Approach.”

What is a Safe System approach?

Simply put: If Vision Zero – safe mobility for all – is our goal, then the Safe System approach is how we get there.

The Safe System approach – sometimes referred to as Safety by Design – has long been used in the fields of aviation, shipping, rail transport and occupational health. Beginning in the 1990s, the concept started to be applied to road safety too, and, over time, is proving successful. 

Here’s a high-level overview of the differences: The traditional roadway safety approach is built on an implicit assumption that people can be trained (encouraged, educated, and/or enforced) to behave safely all the time. The Safe System approach, on the other hand, recognizes that people will inevitably make mistakes (because humans are fallible, after all). So, the Safe System approach anticipates these inevitable mistakes by designing and managing systems – road infrastructure, vehicles, and related policies – to keep the risks of mistake less severe. And when a mistake does lead to a crash, a safe system is one that lessens severe impacts on the human body. So, crashes will happen, but they’re less likely to result in severe injuries or deaths.

>> We recommend reading this Safe System report from the Organization for Economic Cooperation and Development (OECD).

The Safe System approach is human-centered, placing safety as the priority. It does not accept trade-offs between human lives and other priorities. This takes more than a commitment to Vision Zero, and more than a resolution or a plan. It takes a shift in business-as-usual, a willingness to change the status quo of how we conceive of and make decisions related to the transportation system, which should afford everyone the right to safe mobility. 

Key Principles of the Safe System Approach

The Safe System approach to roadway safety addresses the systems, policies, and physical environment — through the design of the roads, vehicles, speeds and policies —  in ways that are human-centric.

“Safe Systems is fundamentally a different way of looking at the problem, and once we see things differently, it allows us to look for solutions a little differently,” explained Mark Doctor, a Safe System expert at the Federal Highway Safety Administration (FHWA). Read more here.

The graphic above shares a high level summary of how the Safe System approach differs from the traditional approach. Following is our brief overview of these key principles, along with actionable examples for how these principles translate to Vision Zero efforts: 

1) Prevent Crashes —> Prevent Death & Serious Injuries

The Safe System approach acknowledges that humans will inevitably make mistakes. So, while we want to prevent crashes, we also know that we cannot stop all crashes. The greatest focus is on helping to lessen the severity of crashes, so that they do not result in serious injuries or deaths. 

This manifests itself in how a community sets its goals, strategies, priorities and funding approach. For instance, if we treated all crashes the same, a lot of resources would go toward problems that are most likely resulting in fender benders, rather than focusing on more serious, life-altering types of crashes.

Another example of operationalizing this principle is Vision Zero’s focus on “vulnerable” road users, or those outside of motor vehicles – people walking, biking and riding motorcycles – who are more likely to be severely injured or killed in a crash, and who are far over-represented in fatal and serious crashes. Therefore, greater attention and resources should be put toward improving the safety of vulnerable road users, given the greater harms (and considering the general societal benefits of more people walking and biking, in terms of health/physical activity, cost savings and environmental benefits).

Source: Tacoma, WA Vision Zero Action Plan

Takeaway for Vision Zero planning: Map out your community’s high risk areas in a High Injury Network (HIN) and prioritize actions and investments in areas that not only pose the highest safety risk, but also disproportionately impact vulnerable road users like young people, seniors who don’t drive, those living in lower income communities, or other factors. For example, Philadelphia overlaid its High Injury Network over community demographics and found that fatal or serious injury crashes were 3x more likely to occur in areas of the city where residents are living on lower incomes. So, in their Action Plan they list “equitable traffic safety investments in neighborhoods needing them most” as a core Vision Zero goal for their community. 

Source: Philadelphia Vision Zero Action Plan

Takeaway for Vision Zero implementation: Effectively lowering speeds of motor vehicles - especially in places where people are walking and biking – is an important strategy to prevent serious deaths and injuries. The speed at which crashes occur (as well as the differences in size/weight) affect the severity of the crash. So, two cars crashing at very low speed is more likely to be an unfortunate, but manageable, fender bender. While a crash between a vehicle traveling at high speeds and a person walking is likely to be far more serious. We can manage speeds for safety (more below).

2) Improve Human Behavior → Design for Human Mistakes/Limitations

This principle also builds off the fact that we cannot ensure perfect behavior. But we can design our systems in ways that encourage safer behavior and, failing that at times, we can design systems that are more “forgiving” of mistakes. For instance, this might look like designing Complete Streets with protected bike lanes, connected sidewalks and high-visibility crosswalks, and ample room for people walking, biking and riding transit, as well as lowering speeds with traffic calming measures, such as road diets, speed humps, leading pedestrian intervals and retiming signal progressions for safer speeds. 

These countermeasures can play a critical role in influencing people’s driving behavior – and far more than billboard campaigns, radio ads or other education efforts focused on trying to reach everyone on the roads individually. 

So, while there is still the need to educate people to understand and follow safety rules, we cannot expect to educate (nor enforce) our way out of the pressing roadway safety crisis. The Safe System approach helps us to focus on changing the upstream systems – including the design of our communities and roads, how we set and manage speeds, how vehicles are designed and permitted to operate, what transportation options exist where and for whom, and how norms and rules are set for moving about.

Note that this is an important distinction from the traditional approach to roadway safety, built on the “E’s” foundation of Engineering, Education, Enforcement, etc. which has focused significantly on encouraging individual responsibility, or more downstream, versus an upstream approach. Read more in our Evolving beyond the Es piece. 

Takeaway for Vision Zero planning: Rather than developing your Vision Zero plan on the traditional E’s approach, this is a chance to set a new foundation with emphasis on Safe System fundamentals. Philadelphia’s first Vision Zero plan in 2017 was built on a typical E’s basis, as most safety work has been for the past century, then it was updated in 2020 to a strong Safe System foundation, which included, but also recognized limitations, of education and enforcement efforts, while emphasizing safe street design and speed management strategies.

Philadelphia’s 2017 Vision Zero Action Plan compared to their 2020 plan

Takeaway for Vision Zero implementation: Examples include installing alcohol interlock systems in vehicles of repeat offenders of drunk driving for more certain safety results, rather than relying on soft “encouragement” campaigns that may or may not work. Another is replacing a stop sign with a well-designed roundabout, or traffic calming circle, which better deters high speeds through an intersection because the latter is a physical deterrent. This is also an example of a more self-enforcing roadway design, recognizing that the design of the built environment has significant influence on how people behave; and this has the additional benefit of reducing the need for reactive, punitive traffic stops by investing in more proactive, preventative safe road design.

3) Control Speeding —> Reduce System Kinetic Energy

Much of the success of the Safe Systems approach rests on managing speeds for safety. It’s actually pretty simple: As kinetic energy increases, so does the probability of crashes and the severity of those crashes. So, if you lower the kinetic energy — especially amongst differently sized road users (ex: a person walking vs. a person driving an SUV) — then you lower the chance of and severity of crashes. 

We have many strategies to reduce kinetic energy, but we are not using them often nor fully enough. For instance, we can slow people down by re-designing streets, adding traffic calming measures, reducing speed limits, and leveraging technology that limits high speeds. These are all priorities within the Safe System approach, and, simply put, we won’t significantly advance Vision Zero without showing more political will to slow speeds on our streets.

Note that we’re talking about more than controlling “speeding” here. A Safe System approach focuses on how the systems we’ve set up either encourage or discourage safe speeds. For instance, certain road designs incentivize high speeds (ex: streets with multiple, straight, wide lanes and poor, low-visibility intersections for people crossing the street on foot) and other designs discourage high speeds (ex: streets with fewer and narrower lanes, roundabouts and speed humps). 

We can and should do more to invest in upstream strategies that deter unsafe speeds – such as redesigning the roadways with proven traffic calming measures and requiring safety features in vehicles – rather than over-depending on downstream, individual-focused strategies, such as PR campaigns telling drivers to “be safe” or trying to have police presence everywhere in a community.

>> Check out this comprehensive speed management report from advocacy group Walk San Francisco, which focuses on upstream solutions. Rather than over-depending on education or enforcement, the report uplifts system-level changes, including re-designing roads to physically discourage high speeds and lowering speed limits to better fit the context and needs of the communities. 

Takeaway for Vision Zero planning:  A strong Vision Zero Action Plan will include speed management as a top priority, without an over emphasis on enforcement. The Denver Regional Council of Governments’ (DRCOG) action plan emphasizes speed reduction strategies, such as adding speed humps, bulbouts, chicanes and mini traffic circles, as well as reducing travel lane widths to encourage lower speeds. Tacoma, WA’s Action Plan also prioritizes installing traffic calming features systemwide to encourage safer speeds. And, notably, they set a clear schedule – addressing at least one arterial street per year – helping to encourage focus and accountability.

Source: DRCOG's Regional Vision Zero Action Plan

Takeaway for Vision Zero implementation: Combinations of proven strategies exist to manage speeds for safety, including adding traffic calming measures, lowering speed limits, increasing awareness of speed limits with more signage, and controlling speeds in vehicles. Read more from NACTO, research, and examples from U.S. cities.

4) Individuals are Responsible → Share Responsibility

Another guiding principle of Vision Zero is that responsibility for a Safe System is shared. This means that while individuals do have a responsibility to act with care for themselves and others, there is also, importantly, shared responsibility amongst those who design, build and manage the transportation systems. This includes not only the planners and engineers working on the built environment, but also elected officials who oversee policy decisions that directly influence safety. Similarly, vehicle manufacturers and regulators share responsibility for designing vehicles in ways that bolster safety. 

“Nothing will change in road safety without strong and visionary leaders,” as stated in the OECD Safe System report. For the most part, we know which tools and strategies are most effective in ensuring safe mobility – a combination of policy changes, modernized road designs, and advanced technologies exist today to save lives. What is needed most now is strong political leadership and a sense of urgency to make change. Read more about how Vision Zero is achievable.

Unfortunately, too often, political leadership is lacking, as many electeds fear the pushback that comes when making change. Examples include changing street designs to prioritize safety over speed (even low-cost, quick-build projects), lowering speed limits (see what they did in Seattle), and requiring vehicles to include the designs and technologies that are known to improve safety (and are already required in many countries).

Takeaway for Vision Zero planning: Find ways to bolster your Vision Zero Action Plan with political commitment and broad, deep internal buy-in amongst stakeholders. Developing a strong Vision Zero Task force, including a range of representation and perspectives, is important to touch on the many components that influence - and are influenced by – transportation safety decisions. For example, Taskforce members are likely to be more engaged and take this work seriously if top leaders make it a priority; this could mean the Mayor attends the Taskforce’s kickoff meeting to express her or his commitment to the Plan, then continues to send high-ranking staff to participate in ongoing work. 

Source: Tacoma Vision Zero Action Plan

Takeaway for Vision Zero implementation: Proven safety strategies exist to improve various transportation systems and policies, though many are under-utilized. See resources shared by USDOT, including some geared for smaller communities and for regional entities, such as Metropolitan Planning Organizations. 

5) React Based on Crash History —> Proactively Identify & Address Risks

A Safe System moves beyond a rearwards, reactive response to roadway safety problems. Instead, it takes a more proactive and preventative approach. 

This entails building on the initial step of reviewing crash maps showing past problems to focus on trends and patterns to identify likely, future problem areas, then implementing strategies to prevent severe crashes before they happen. This means determining, analyzing, and addressing the underlying risk factors that influence dangerous actions: the where, how, and why serious crashes happen.

Too often, severe crashes are seen as distinct tragedies that happen independently of each other. But the reality is that these tragedies likely share common traits, are predictable, and can be prevented. There are root causes, or risks, in the systems that can be changed. A key way to be more proactive in addressing safety risks is to identify streets (or locations) where past problems have occurred and analyze their design features to identify other similarly designed areas where problems are likely to occur and proactively implement these solutions systemwide. See examples of cities instituting this approach to more proactively and systemically identify and address top risk factors and mitigate potential crashes and severity with improved road design and policies. 

Another example of being more proactive is addressing the growing danger of mismatched size and physical vulnerability among road users. Pickup trucks and SUVs – the fastest-growing vehicle sales in the country – are two to three times more likely than smaller personal vehicles to kill people walking in a crash. Vehicle manufacturers can and should institute safety features to lessen this known, predictable risk; we need an upstream approach to safety, rather than setting people up to have devastating, unintended tragedies on the roads. 

Takeaway for Vision Zero planning:  Build in steps to assess and evaluate the efficacy of safety countermeasures. For example, the Denver Regional Council of Governments’ (DRCOG) action plan calls for analyzing crashes to better understand factors and to inform future safety strategies, including proactively addressing street design changes before problems occur.

Source: DRCOG Regional Vision Zero Plan

Takeaway for Vision Zero implementation: When addressing dangers, such as unsafe speeds, on a single, problematic corridor, also put the time and resources into analyzing whether the same (or similar) conditions exist on other corridors in your community. This is a chance to proactively – and more efficiently – address roadway safety system wide, rather than waiting for a tragedy to occur and fixing a design problem after the fact. See more examples.

Equity Imperatives in Shifting from “E’s” to Safe System approach

Another benefit of a Safe System approach is that it can provide not only a more effective framework, but also, importantly, a more just foundation for roadway safety work. 

Transportation planning in the U.S. has largely been built on a century-old approach to safety -  often called the “E’s” – with a focus primarily on Engineering, Education, Enforcement & Emergency Services. While these (and other)  individual E’s have a role to play, they need to be better evaluated for shortcomings and held to higher standards, especially in terms of effectiveness and equity.

It is time to evolve beyond the E’s – read more. One reason is that, for too long, inequitable strategies have been used, reinforcing inequitable outcomes. For instance, too often, racialized enforcement has been justified in the pursuit of “safe streets,” and, increasingly, communities want to depend less on this reactive, punitive strategy. Read more about how many people are rethinking the role of enforcement in traffic safety: here and here

Meanwhile, the “E” of engineering a safe built environment has been under-utilized, particularly in Black, Latinx, Indigenous, and other racialized or marginalized communities, resulting in poor road design, poor land uses, and disparities in health and safety outcomes. Vision Zero’s Safe System approach should be used to focus more on self-enforcing road design and instituting effective and equitable strategies and policies, not just propping up the status quo E’s approach.

Vision Zero Network diagram highlight the impact of the Safe System approach on equity

Why Vision Zero & the Safe System approach?

So, why should communities invest in shifting to a Safe System approach? And why now? 

With over 46,000 people dying on our roadways each year, we still have a long way to go in reaching the goals of Vision Zero. When compared to other OECD nations, many boast roadway death rates at a fraction of the U.S. toll. So, clearly the status quo of how we do roadway safety work is not working well enough. 

The Safe System approach – when implemented fully and strategically – is proven to work. Research from WRI Ross Center for Sustainable Cities and the Global Road Safety Facility of the World Bank finds that the most effective way to prevent traffic deaths is this systemic approach. Their analysis of 53 countries found that those taking a Safe System approach have achieved the lowest rates of traffic fatalities and the greatest reduction in fatality levels over the past 20 years. 

Increasingly, more nations are recognizing the long-term efficacy, including the U.S. In fact, the U.S. Department of Transportation (USDOT) recently adopted the Safe System approach and set its first-ever national goal of zero roadway fatalities. 

As U.S. Transportation Secretary Pete Buttigieg shared during the release of the USDOT’s first-ever National Roadway Safety Strategy

“People make mistakes. But human mistakes don't always have to be lethal. And in a well-designed system, safety measures make sure that human fallibility does not lead to human fatalities. That's what we will be doing for America's roads with the National Roadway Safety Strategy and the safe system approach that it embraces” (full comments here).  

Ultimately, adopting the Safe System approach is about making change. It’s about recognizing that we need to do more than play in the margins. We need a paradigm shift. 

Whether you're a new Vision Zero community just starting out in your planning process or a more established city scaling up its efforts, the shift to a Safe System is an important step in developing our transportation systems and policies to foster safety in effective, inclusive ways. The strategies exist -- such as proactively identifying crash risk factors and adding traffic calming measures to slow speeds. Now, we need the political and public will to embrace and implement the Safe System approach and work towards a brighter, safer, and more equitable future in mobility for all. 

Interested in learning more? Check out these additional resources: 

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