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Public Roads - Winter 2022

Winter 2022
Issue No:
Vol. 85 No. 4
Publication Number:
Table of Contents

Making our Roads Safer through a Safe System Approach

by Mark Doctor and Chimai Ngo
"An urban street with sidewalks lit up at night with a mid-block pedestrian crosswalk and median refuge island. Photo Source: FHWA."
The United States is beginning to adopt a Safe System Approach to address roadway safety challenges. 

Achieving the vision of eliminating deaths and serious injuries from the Nation’s roads may seem daunting with traffic fatalities in the United States stubbornly remaining between 32,000 and 39,000 annually for more than a decade. To make meaningful progress, changes are needed in how to think about the traffic safety problem and the approaches to solve the problem. The Safe System Approach is being applied with great success in a growing number of nations and cities around the world and has now taken hold in the United States.

The Safe System Approach has origins in Sweden through its Vision Zero program and with the Sustainable Safety program in the Netherlands. These early adopters experienced impressive decreases in road traffic fatalities—each with at least a 50-percent reduction in fatalities between 1994 and 2015. The concept has spread to other countries in Europe and beyond with notable success in Australia and New Zealand.

The Safe System Approach requires a culture that places safety first and foremost in road system investment decisions. 

In comparison, fatalities in the United States decreased by less than 13 percent during the same 1994–2015 period. International success with the Safe System Approach gives promise that the United States may also be able to achieve similar positive safety outcomes. With growing momentum and initiatives being taken by agencies across the country, the United States has started on the journey toward implementing a Safe System. 

The vision of eliminating fatalities and serious injuries on the Nation’s roads are shared through such parallel initiatives as Vision Zero, Toward Zero Deaths, and Road to Zero. All three efforts acknowledge the importance of implementing the Safe System Approach in different contexts. With Vision Zero, local communities are applying the Safe System Approach with a focus on safe mobility for all road users, especially those in the underserved communities. The Vision Zero Network is working with communities committed to reaching their Vision Zero goals. Many State agencies have adopted zero-deaths goals in their Strategic Highway Safety Plans (SHSP), using the Safe System framework from the report Toward Zero Deaths: A National Strategy on Highway Safety. The American Association of State Highway and Transportation Officials (AASHTO) has been leading Toward Zero Deaths efforts since 2009. A third effort, the Road to Zero Coalition, under the leadership of the National Safety Council, also identified as a main initiative the need to prioritize safety by adopting a Safe System Approach and to create a positive safety culture.

Safe System Approach Principles and Elements 

The Safe System Approach starts with a mindset that it is unacceptable to allow deaths and serious injuries to occur on the roads. It also acknowledges that road users are human beings and that humans will inevitably make mistakes. On the roads, those mistakes may lead to crashes. The goal of “zero” is to eliminate fatal and serious injuries, not to eliminate crashes. This is a very important distinction for understanding how the road safety problem is viewed under the Safe System Approach. To achieve zero deaths and serious injuries, when crashes do happen, they must be managed so that the kinetic energy exchange on the human body is kept below the tolerable limits for serious harm to occur. This important principle is at the core of applying a Safe System Approach in designing and operating the road system. Human error is to be expected so the road infrastructure and vehicle technology must be designed and operated so that deaths and serious injuries are engineered out. This may be achieved first by reducing the risk of error occurring and secondly by keeping collision forces on the human body within tolerable levels, when crashes do occur, by managing speed and crash angles to reduce injury severity.

The Safe System Approach considers five elements of a safe transportation system—safe road users, safe vehicles, safe speeds, safe roads, and post-crash care—in an integrated and holistic manner. Achieving zero traffic deaths and serious injuries requires strengthening all five elements. A Safe System cannot be achieved without all five elements working in synergy. Within a Safe System Approach, weaknesses in one element may be compensated for with solutions in other areas. A true systems approach involves optimizing across all the elements to create layers of protection against harm on the roads.

  • Safe Road Users—The safety of all road users is equitably addressed, including those who walk, bike, drive, ride transit, or travel by other modes.
  • Safe Vehicles—Vehicles are designed and regulated to minimize the frequency and severity of collisions using safety measures that incorporate the latest technology.
  • Safe Speeds—Humans are less likely to survive high-speed crashes. Reducing speeds can accommodate human-injury tolerances in three ways: reducing impact forces, providing additional time for drivers to stop, and improving visibility.
  • Safe Roads—Designing transportation infrastructure to accommodate human mistakes and injury tolerances can greatly reduce the severity of crashes that do occur. Examples include physically separating people traveling at different speeds, providing dedicated times for different users to move through a space, and alerting users to hazards and other road users.
  • Post-Crash Care—People who are injured in collisions rely on emergency first responders to quickly locate and stabilize their injuries and transport them to medical facilities. Post-crash care also includes forensic analysis at the crash site, traffic incident management, and other activities.

Six Foundational Principles for Understanding and Applying the Safe System Approach: 

Deaths and serious injuries are unacceptable—While no crashes are desirable, the Safe System Approach emphasizes a focus on crashes that result in death and serious injuries. Regardless of road users’ socio-economic backgrounds, their abilities, and the modes they use, no one should experience deaths or serious injuries when using the transportation system.

Humans make mistakes—Road users will inevitably make mistakes, and those mistakes can lead to crashes. The Safe System Approach expects the road system be planned, designed, and operated to be forgiving of inevitable human mistakes, so that serious injury outcomes are unlikely to occur.

Humans are vulnerable—Humans have limited ability to tolerate crash impacts before harm occurs. Although the exchange of kinetic energy in collisions among vehicles, objects, and road users has multiple determinants, applying the Safe System Approach involves managing the kinetic energy of crashes to avoid serious injury outcomes.

Responsibility is shared—All stakeholders (transportation system users and managers, vehicle manufacturers, etc.) must work collaboratively to ensure that crashes don’t lead to fatal or serious injuries.

Safety is proactive—Transportation agencies should use proactive and data-driven tools to identify and mitigate latent risks in the system, rather than waiting for crashes to occur and reacting afterwards.

Redundancy is crucial—Reducing the risk of severe crash outcomes requires all parts of the system to be strengthened, so that if one element fails, the others still protect road users.

"Graphic showing a wheel with five sections depicting five Safe System elements: Safe Road Users, Safe Vehicles, Safe Speeds, Safe Roads, and Post-Crash Care. Around the wheel are six Safe System principles: Death/Serious Injury is Unacceptable, Humans Make Mistakes, Humans are Vulnerable, Responsibility is Shared, Safety is Proactive, and Redundancy is Crucial. Image Source: FHWA."
The Safe System Approach principles and elements.
"Crowds of people cross a busy intersection in Manhattan with a colorful sunset in the background skyline. Photo Source: © deberarr /"
Implementing a Safe System Approach requires finding equitable solutions for many road users.

Providing a Safe System for All 

Progressing with implementation of a Safe System requires equitable solutions. By examining road safety data with correlations to community sociodemographic characteristics, many agencies have found that higher risks of crash deaths are concentrated in lower-income neighborhoods where exposure to traffic may be higher and past investments in safety programs and infrastructure may be lower. Prioritizing these communities for implementation of the Safe System Approach can offer substantial safety improvements and close the gap between risk in well-invested and underserved neighborhoods.

“Centering equity within Vision Zero efforts is vitally important and timely,” says Leah Shahum, founder and executive director of the Vision Zero Network. “Communities across the country are struggling with social, racial, and economic inequities, including disparities within the transportation realm. Low-income communities and communities of color often bear a disproportionate burden of traffic-related injuries and fatalities. We cannot reach zero traffic deaths without addressing issues of equity.”

Notable Safe System Practices: California, Florida, and Washington 

Numerous transportation agencies across the United States have already begun to implement and institutionalize Safe System principles. While these agencies are at different stages of implementation, they all have pivoted to this approach with the goal of making positive and significant differences in safety. Three such States are highlighted here. Other articles in this issue of Public Roads will further detail these efforts.

To integrate the Safe System Approach at the program level, the California Department of Transportation (Caltrans) introduced a new safety paradigm in 2020. The agency established the new Division of Safety Programs and incorporated four safety-focused initiatives or pillars into its SHSP. One of the pillars calls for implementation of a Safe System Approach. The institutional commitment to the Safe System Approach has been the foundation for many positive cultural and programmatic changes within the agency, one of which is the establishment of the Pedestrian Systemic Safety Improvement Program that had been started as a pilot in 2016. The program integrates Safe System elements and principles into a systemic approach to further the goal of zero deaths.

“Caltrans has adopted the Safe System Approach and is institutionalizing it department-wide as part of our new approach to safety,” says Rachel Carpenter, the chief safety officer for Caltrans. “Our updated Strategic Management Plan reflects our commitment to the Safe System Approach and we are actively working to incorporate Safe System principles and elements across all divisions and the entire project lifecycle.”

"The title at the top of this graphic reads “California Strategic Highway Safety Plan Pivot – Institutionalize Four Guiding Principles.” A logo on the right-hand side shows a two-lane road wrapped around the shape of California and reads “California Safe Roads.” The four principles are shown as follows. The first has a simple line drawing of check symbol over a ribbon shape inside a circle that reads “Double down on what works.” The second has a lightbulb inside a circle and reads “Accelerate advanced technology.” The third shows a clipboard with a checklist inside a circle and reads “Implement Safe System Approach. And the fourth shows a set of scales inside a circle and reads “Integrate equity.” Image Source: © 2021 Caltrans."
Implementing a Safe Systems Approach is one of the four pillars of Caltran’s Strategic Highway Safety Plan.

The Florida Department of Transportation (FDOT) and its safety partners work toward their Vision Zero goal of zero fatalities and serious injuries through the State SHSP, which serves as the overall framework of efforts and activities to improve safety toward that ultimate goal. Florida’s 2021–2025 SHSP introduced the Safe System Approach to address safety in an integrated manner with a collective commitment of time, talent, and resources to new priorities, strategies, and enhanced partnerships. Because Florida experienced a 27-percent increase in fatalities at intersections between 2015 and 2019, intersections are identified as an emphasis area within the SHSP. Among the focused strategies identified in the SHSP is the systematic use of Intersection Control Evaluations to implement innovative designs such as roundabouts and reduced left-turn conflict intersections on projects that offer opportunities to make intersection improvements.

Alan El-Urfali, the State traffic services program engineer for FDOT, says, “Including the Safe System for intersections assessment framework into our Intersection Control Evaluation process can help inform designers on better intersection design choices that proactively take steps to reduce fatal and serious crashes at intersections.”

The Washington State Department of Transportation (WSDOT) recognized that to achieve its zero-deaths goal, appropriate policies must be in place to implement a Safe System Approach throughout the planning, programming, design, and operations sections of its department. WSDOT leverages its SHSP and Target Zero efforts to align Safe System principles across discipline areas and provide direction throughout capital and operational program elements. WSDOT changed the safety subprogram to emphasize proactive safety projects; 70 percent of its funds are targeted towards the crash prevention category.

“Adopting a Safe System Approach led WSDOT to change its philosophy to focus on fatal and serious rather than all crashes,” says John Milton, the State safety engineer at WSDOT. “Our focus also shifted to managing kinetic energy and addressing safe speeds through data-driven and performance-based approaches that incorporate using context-sensitive design.”

This philosophical shift has resulted in many positive changes, among which are updated safety policies and associated budget programing, the creation of the Active Transportation division to recognize all transportation modes, updated design and traffic manuals to incorporate context-sensitive design and operations, a draft policy framework for injury minimization through speed management that serves as a model for any jurisdiction in the State, incorporation of safety for all modes in the new Transportation Systems Management and Operations plan currently under development, and incorporation of Level of Traffic Stress metrics for active transportation in its definition of asset conditions to be used in programming preservation funds.

One Death is Too Many: Portland, OR 

The city of Portland, OR, committed to Vision Zero when the city council unanimously passed a resolution in June 2015 and adopted a Vision Zero Action Plan in December 2016. Portland’s reputation as a walkable, bikeable, and livable city was strong motivation to address a rise in the percentage of pedestrian deaths and steady percentage of bicycle deaths. Data indicated that while pedestrian trips account for about 9 percent of all trips in Portland, pedestrians were nearly one-third of the traffic-related deaths.

Portland’s Vision Zero Action Plan also recognizes the need for working toward equitable communities and prioritizing infrastructure investments on the most dangerous streets in traditionally underinvested communities. Using a data-driven approach, Portland was able to identify that although deadly or serious injury crashes can happen anywhere, more of them happen on certain street types. Wide, fast arterials with multiple lanes in each direction had a disproportionate number of traffic deaths. Also, many of the streets went through lower-income neighborhoods where people rely heavily on walking and transit. In Portland, more than half of deadly crashes occurred on just 8 percent of city streets. Improving this identified “high-crash network” is a central element of Portland’s Vision Zero strategy.

A fundamental principle of the Safe System Approach is that people make mistakes. Impairment, speeding, distracted driving, aggressive driving—these are all discouraged behaviors and the Portland Vision Zero Action Plan includes coordinated actions to deter them. But the plan also acknowledges the role that street design plays to encourage and enable safe behaviors. Streets should discourage unsafe driving by design. Safer street designs can slow down traffic, provide visual cues that make it clear when different user groups share the space, and when needed, provide separation between the user groups when vehicular operating speeds are incompatible for sharing space with other users. Adhering to these design principles keep all people safer—even when they make mistakes.

With Portland’s data indicating a disproportionate number of pedestrian deaths, slowing vehicular speeds is a critical part of the city’s Vision Zero plan. A person’s chances for surviving a crash increase dramatically with lower speeds. A pedestrian struck by a person driving at 40 miles (64 kilometers) per hour is 8 times more likely to die than one struck at 20 miles (32 kilometers) per hour. Managing speed is critical, and Portland has taken action by setting appropriate speed limits, designing streets to support safe speeds, and operating safety camera programs to enforce speed limits.

The Portland Vision Zero Action Plan recognizes that improving safety requires a suite of actions spanning policy, infrastructure, education, and enforcement. This aligns closely with the Safe System principles of shared responsibility and having redundancy in the system.

"This drawing shows a roadway in an urban neighborhood with the following characteristics: two lanes in each direction, protected turn lanes, dedicated bicycle lanes, a landscaped median, wide sidewalks, and a pedestrian crossing with traffic lights. Photo Source: © Portland Bureau of Transportation."
Portland, OR, is known as a walkable and bikeable city, so its Vision Zero Action Plan includes a focus on safety and equity for all road users.

Many of the strategies identified in Portland’s Vision Zero Action Plan align along the elements of the Safe System Approach: 

Safe Users. 

  • Traffic Safety Education programming
  • Safe Ride Home Partnership Program
  • Guidelines for later start times of parking enforcement to encourage impaired drivers to leave their car overnight (without having to worry about getting ticketed or towed)

Safe Speeds

  • Safety cameras
  • Multimedia education campaign focusing on the human impact of speed

Safe Roads

  • Use street safety design elements on the high-crash network, which accounts for more than half of Portland’s deadly crashes
  • Redesign streets to include landscaped medians, limited left turns, buffered bike lanes, enhanced bus transit, and additional crosswalks

What’s Ahead of Us? 

Creating a Safe System is a journey that will take time, commitment, and collaboration across disciplines. The Federal Highway Administration and its stakeholders across the transportation community are acting now to advance the Safe System Approach, making decisions guided by the underlying principles, and promoting implementation across the Nation. FHWA is making strides to advance the Safe System Approach through publications and outreach materials, including an overview flyer and awareness presentation. FHWA has issued several reports, including Integrating the Safe System Approach with the Highway Safety Improvement Program (FHWA-SA-20-018) and Safe System-based Framework and Analytical Methodology for Assessing Intersections (FHWA-SA-21-008). FHWA has also published a primer on the Safe System Approach for pedestrians and bicyclists. These reports can be found on FHWA’s Zero Deaths website at, which provides resources on the Safe System Approach as well as material related to zero-deaths goals and strategies. Additionally, organizations and initiatives, including the Road to Zero Coalition, Toward Zero Deaths, and Vision Zero Network, offer valuable resources and references. The Institute of Transportation Engineers also offers a comprehensive website of technical resources for agencies looking to bring a Safe System Approach to their community.

As the United States advances along the journey to implement a Safe System to eliminate traffic deaths and serious injuries, everyone is a stakeholder with an important role.

Mark Doctor is a senior safety and design engineer in the FHWA Resource Center. Mark provides technical services and advances technology deployment in performance-based safety and design areas. He holds an M.S. degree in transportation engineering from the University of Florida.

Chimai Ngo is a program manager for zero deaths, safety culture, and transportation safety planning initiatives in the FHWA Office of Safety. She holds a master’s degree in planning from the University of Virginia.

For more information, visit, or contact Chimai Ngo at or Mark Doctor at