CHAPTER 2

Safe System Policy

Safety policy plays a critical role in fostering a Safe System. Policies establish the rules that govern what is allowed by law or by custom. They provide legal and regulatory legitimacy for changes in safety procedures and practices. Moreover, Safe System policies impact safety work at local, regional, and state levels of government. For example, municipal policies might require the provision of a minimum number of parking spaces per square feet of various development types, which can induce motor vehicle traffic and render municipal commercial areas less safe for road users (Dumbaugh and Rae 2009). On the other hand, state laws that govern local municipalities might prohibit the use of speed safety cameras, a proven safety countermeasure, especially when equitably implemented in communities (Ralph et al. 2022). Pedestrian safety is shaped by federal regulations around the pedestrian detection and collision avoidance capabilities of motor vehicles sold in the United States (Mallory et al. 2023).

As Swanson and Bhadwal (2009) observed, and as shown in Figure 3, all policies proceed through a design phase and an implementation phase. As an illustration of these phases, consider posted speed limits. The federal government can define how speed limits may be set, and local or state lawmakers define the penalties for drivers who exceed the posted speed limit by a certain amount. Police officers are then tasked with implementing the policy by choosing which speeding drivers to stop and deciding how precisely to implement the policy (e.g., determining whether the speeding infraction was worthy of a warning or a speeding ticket). Together with additional speed-related infractions, the local government and its police department will decide whether speeding is a pressing issue and thus worthy of high or low enforcement priority.

Currently, transportation safety policies tend to focus on providing protection for vehicle occupants and are organized around active measures, ones that rely on individual road users to adopt safe behaviors such as requiring people to wear seat belts or motorcycle helmets. However, policies could also advance population-level harm-reduction practices (Ederer et al. 2023) such as requiring location-based speed limiters in all commercial and private vehicles and in vehicle designs like adequate direct vision for large vehicles to minimize serious crashes with vulnerable road users. Before introducing novel safety policies, policymakers could enhance policy compliance by sharing the reasoning underlying a policy and outlining its potential benefits (see Communications and Messaging in Chapter 1).

By not solely relying on individuals to adopt safe technologies and behaviors and instead providing technology, equipment, and infrastructure that offer reliable protections to road users, Safe System policies can vastly improve population-level safety and related health and environmental concerns (De Nazelle et al. 2011). For example, barrier-protected bicycle lanes provide reliable protection for people riding bicycles and can temper drivers’ speeds by perceptually narrowing the travel lane (Schlossberg 2022).

Population-impacting safety policies are necessary and possible. For example, the state of California updated its traffic impact assessments to focus on land-use arrangements that could

Source: Adapted from Creating Adaptive Policies: A Guide for Policymaking in an Uncertain World (Swanson and Bhadwal 2009).

significantly reduce vehicle miles traveled (VMT) rather than concentrating on managing drivers’ delay using level of service (LOS) metrics (Lee and Handy 2018). Moreover, as the Parking Reform Network is demonstrating, several states and thousands of municipalities across the United States are modifying their land-use ordinances to allow for greater flexibility in providing car parking (Parking Reform Network 2024). Further, NHTSA is updating its New Car Assessment Program (NCAP) to consider the implications of vehicle mass, height, and design on the safety for vulnerable road users (NHTSA 2023b).

Unfortunately, as established by the U.S. Congress, some federal-aid funding programs disallow funding to be used to maintain safety infrastructure. The inability to rely on federal funds to maintain infrastructure may result in states disallowing the installation of certain countermeasures (e.g., rectangular rapid flashing beacons, sidewalks, cable-median barriers) on state-owned roadways (Jane Gibson and Marshall 2022).

Additionally, state agencies and governments regularly aim to provide high degrees of motor vehicle mobility throughout a corridor, yet state and local agencies often permit dense concentrations of driveways that provide high degrees of access to land developments. However, in a Safe System, roads and streets do not provide mobility and access within the same corridor (Corben 2022). Not only that, state and local agencies tend to employ vehicular LOS as performance measures for intersections and segments, but a Safe System calls for using survivable operating speed measures to assess facilities’ performance (Kumfer et al. 2023).

2.1 Key Policy-Related Strategies

An array of policies could influence Safe System work at the local, regional, and state levels. For example, a community might have a local policy that establishes default 20 miles per hour (mph) posted speed limits on local streets unless otherwise specified. Examples of types of policies to review at the local, regional, and state levels include those outlined in Table 1.

Table 1 presents examples of specific policies to review and discern their alignment with creating a safe transportation system.

To apply the principles of a Safe System in the context of policymaking, the following three policy strategies can encourage practices that contribute to a Safe System:

1. Advance adaptive safety policies.

   No matter the level of legal authority or the strength of the policy guidance, in an ever-changing environment, ideal policies are adaptive rather than inflexible—that is, policies should have

Table 1. Types and examples of safety policies.

Source: Adapted from Guide to Developing a Vision Zero Plan (LaJeunesse et al. 2020). Collaborative Sciences Center for Road Safety. https://www.roadsafety.unc.edu/research/projects/2018r17.

1. the ability to change in response to disruptions and alterations in funding, available technology, extreme weather events, demographic shifts, changes in travel patterns, and more (Markolf et al. 2019; Marsden and Docherty 2013). Further, those tasked with implementing policies should adopt an explicit learning orientation and gather feedback on policy performance and adjusting policies accordingly (Sterman 1994; Reiman et al. 2015).

   Some changes and disruptions can be anticipated, such as the need to routinely maintain bridge and street infrastructure. Other changes will be unanticipated; therefore, implementing redundancies that can back up failing parts of the system must be required.

   Methods to proactively respond to anticipated and unanticipated conditions include the following:

   • – Enable automatic policy adjustments that are triggered by anticipated events (e.g., experimenting with quick-build curb extensions during foreseen diminished capital funding).
   • – Schedule regular policy reviews even when the policy is performing as intended so that policies can meaningfully respond to emerging issues (e.g., rising use of drugs while driving) and adjust to changing conditions that could not have been anticipated.
   • – Diversify implemented policies, which makes it easier to contend with changes, by spreading risk across the system (Berkes, Colding, and Folke, 2003) (e.g., simultaneously updating rezoning and Complete Street policies, both of which shape streets’ relationships with surrounding land uses, such as the size of building setbacks and the type of bicycle infrastructure appropriate for specific road classifications).
   • – Decentralize decision-making, which involves granting the authority and responsibility for decision-making to the lowest effective unit of governance, such as setting local speed limits. This often enhances the ability of a policy to perform successfully when confronted with unanticipated events (Swanson and Bhadwal 2009).
2. Build up Safe System–consistent practices and break down inconsistent practices.

   Safe System policies should be designed to break down Safe System–inconsistent practices while building up consistent practices. Too often, policymakers and professionals ramp up the

2. addition of safety measures (e.g., installing separated bicycle lanes along a corridor with a high rate of injuries) without altering policies and practices that increase the risk of severe road-user conflicts (e.g., traffic impact assessments resulting in the addition of turning lanes and widening of driveways, which renders crossing the road more difficult and dangerous). An example of this build-up–break-down approach to Safe System policymaking is allocating revenues generated from speed safety and red-light-running cameras to addressing network gaps in safety infrastructure, especially in areas that have not been involved in decision-making to date. In this case, the unsafe behaviors of speeding and red-light running are actively discouraged, while investment in safe, traffic-calming infrastructure is elevated.
3. Provide reliable and protective system redundancies.

   Safe System policies promote a transition away from layering interventions to providing more reliable, protective redundancies in the system. The popular Swiss cheese model of hazard mitigation shows layers of hole-ridden Swiss cheese illustrating how the layering of different Safe System elements (e.g., safe road users, safe roads, safe speeds) creates system redundancies. However, simply layering safe road users, safe roads, and safe speed elements of a Safe System on top of one another does not guarantee protection for road users. For example, installing new advisory speed plaques can be argued to address the safe road users, safe roads, and safe speeds elements of a Safe System, but signs and plaques alone do not provide reliable protection to road users under a Safe System (Williamson 2021; Soames Job, Truong, and Sakashita 2022).

   Consider a policy that (1) requires location-based speed limiters in private vehicles—e.g., Washington, DC’s “Strengthening Traffic Enforcement, Education, and Responsibility (STEER) Amendment Act of 2023,” which will pilot test the installation of intelligent speed assist (ISA) in the cars of drivers convicted of criminal aggravated or reckless driving (District of Columbia 2024)—and (2) includes raised pedestrian crossings at transit stop locations. This speed limiter and raised crossing policy combination integrates a reliably protective vehicle technology (i.e., speed governance) with an engineering countermeasure designed to calm car traffic in the realm of crossing pedestrians (i.e., raised pedestrian crossings at transit stop locations). Another example of providing reliably protective system redundancies is pairing automated vehicle lane-keeping technology with longitudinal rumble strips and cable-wire barriers on the edges of rural roads. Furthermore, maintenance of safety infrastructure can be argued to support system redundancy (Große 2023). Road users are protected to the extent diverse system elements are functioning as intended and remain in healthy operating condition.

2.2 Study-Identified Policy Practices

Stemming from policy strategies are more specific safety practices. The example practices outlined in Table 2 align with the strategies of Safe System policies in that they are intended to be adaptive rather than inflexible, to be paired with a scaling down of Safe System–inconsistent policy, and to create conditions within which system redundancies can be implemented and maintained.

The research team identified 19 Safe System–aligned policies from the literature review phase of the research and presented them to safety practitioners via an online survey. Survey participants were asked to rate the safety impact and the financial, social, and political feasibility of each practice, based on their professional experience and institutional knowledge. Participants’ responses on the perceived impact and feasibility of the 19 policy practices can be found in Appendix A.

Table 2. Safe System policy practices.

Example Policy	How Safety Is Improved	Exposure	Likelihood	Severity	Improves IRA, PCC, or CD1	Costs2
Updating NHTSA’s New Car Assessment Program (NCAP) to include pedestrian detection and collision avoidance safety tests	Reduces chances of severe vehicle-pedestrian crashes via detection and crash avoidance technology	−			−	High
Requiring alcohol ignition interlocks installed for all drivers convicted of driving under the influence (DUI)	Prevents repeat offenders from operating a vehicle under the influence and reduces other road users’ exposure to impaired drivers			−	−	Medium
Promoting the installation of technology in private automobiles that records drivers’ distraction, drowsiness, and other forms of incapacitation	Reduces drivers’ impairment levels by monitoring their degree of alertness and reduces other road users’ exposure to impaired drivers			−	−	Low
Establishing maximums in vehicle size (in terms of width, length, height, weight) permitted in areas with high pedestrian activity	Reduces pedestrians’ exposure to harmful kinetic energy levels and vehicle profile heights				−	Medium
Installing seat belt interlocks in vehicles	Secures vehicle occupants to their seats, allowing the vehicle’s crush zone to absorb the kinetic energy transferred in a crash	−	−		−	High
Installing speed governors/limiters in all municipal or state fleet vehicles	Prevents drivers of municipal fleet vehicles from traveling at unsafe speeds and conveys lower operating speed norms	−			−	Medium
Requiring location-based speed limiters in all commercial and private vehicles in areas with high pedestrian activity	Reduces vehicle operating speeds in locations pedestrians are likely to be present	−			−	Low

Example Policy	How Safety Is Improved	Exposure	Likelihood	Severity	Improves IRA, PCC, or CD1	Costs2
Extending graduated driver licensing requirements to include all novice drivers regardless of age	Requires novice drivers to develop safe driving skills via supervised practice	−		−	−	High
Establishing a default speed limit of 20 mph or lower in every business or residential district	When reliably enforced and designed to slow vehicles, can reduce vehicle operating speeds in locations pedestrians are likely to be present	−			−	Medium
Instituting immediate administrative license revocation or suspension (ALR/ALS) for alcohol- and drug-impaired-driving offenses	Deters impaired driving by swiftly removing driving privileges in the event of an infraction			−	−	High
Lowering the blood alcohol concentration (BAC) limit for driving from 0.08 to 0.05	By pairing this policy with public education and reliable enforcement procedures, the policy can lower serious crash risks by reducing the degree of alcohol impairment among the driving population	−		−	−	Low
Installing leading pedestrian intervals with right-turn-on-red restrictions in areas with high pedestrian activity	Reduces right turn vehicle-pedestrian crashes by separating these road users in time			−	−	Low
Instituting a driver license renewal program that requires passing an on-road driving test every 5–10 years	Enhances the likelihood that drivers possess safe levels of visual acuity, perceptual decision-making, and reaction times	−		−	−	High

Note: − = Not applicable.

¹ IRA = injury risk assessment, PCC = professional and community coordination, CD = crash diagnoses.

² Costs correspond to the total financial cost associated with a policy or practice, including labor, equipment, and infrastructure (Low ≤ $100k, Medium = $100k−$1 million, and High ≥ $1 million in total or per year).

In keeping with Safe System principles and policy strategies, the team determined whether each planning practice would reduce road users’ exposure to severe crash types (e.g., run-off-road, head-on, intersection, pedestrian, bicyclist, or motorcyclist crashes) and the likelihood road users would be involved in one or more of these crash types.

• Exposure reflects the number of people with the potential to be involved in serious crash types.
• Likelihood reflects the probability road users will be involved in a crash.
• Severity reflects the chances a crash will result in a fatality or serious injury to the road users involved.
• Improves injury risk assessment, professional and community coordination, or crash diagnoses reflects a practice’s ability to estimate road-user injury risks associated with land use, policy, or engineering interventions; to improve coordination among professionals in different sectors and with the public; or to uncover contributing factors to serious crash events.

Table 2 provides example policies and their change mechanisms (i.e., the steps or processes responsible for improving road users’ safety).

Implementing Safe System Policies

Safe System policies are adaptive, replace Safe System–inconsistent policies, and provide reliable protection to road users through system redundancy. These policies are useful only to the extent they are implemented and maintained.

To begin implementing Safe System–aligned law enforcement practices, consider the following steps and substeps:

1. Identify at least one significant safety problem. Identification and prioritization of a safety problem might be based on the following:
   • – Severity and magnitude of the safety problem
   • – Disproportionate harm caused by the problem and endured by some community members
   • – Importance of addressing the problem to community representatives
   • – Availability of resources to address the problem
2. Ask the following two questions once a safety problem has been identified and prioritized:
   • –To what extent does a proposed practice to address the identified problem align with Safe System–aligned policy strategies?
     • Advance adaptive safety policies
     • Build up Safe System–consistent practices and break down inconsistent practices
     • Provide reliable and protective system redundancies
   • – To what extent does a proposed practice reduce the following?
     • Users’ exposure to serious crashes
     • Likelihood of serious crashes
     • Severity of crashes when they occur
     • Improvements to injury risk assessment, professional and community coordination, or crash diagnoses

For example, in step 1, if a safety team identifies and prioritizes addressing pedestrian injury near schools, they might pursue establishing maximums in vehicle size (in terms of width, length, height, and weight) permitted in areas with high pedestrian activity given the disproportionate harm endured by some community members.

In step 2, a safety team might conclude that a maximum vehicle size policy aligns with the Safe System strategy to provide reliable and protective system redundancies, especially if coupled with robust speed enforcement. The team might also conclude that a maximum vehicle size policy can reduce the severity of crashes when they inevitably occur.

At this point, a team should reflect on whether a selected safety practice (1) aligns with one or more Safe System strategies; (2) can significantly reduce the likelihood of users’ exposure to severe crash forces or enhance injury risk assessment, professional and community coordination, or crash diagnoses; and (3) is feasible given available resources to institute the practice. If the team concludes that all three criteria are satisfied, the practice should be considered for implementation, and the safety team could follow the steps outlined in Table 3. However, if one or more of these three criteria are not satisfied, teams are recommended to start over from step 1 until all three criteria are satisfied.

For illustrative purposes, consider a safety team looking to establish vehicle size maximums (in terms of width, length, height, weight) in areas with high pedestrian activity. Table 3 provides recommended steps to implement this safety practice along with elements to consider within each step.

Table 3. Policy practice implementation steps and example elements.

Conclusion

The shift toward Safe System policy is possible and necessary for the United States to realize zero deaths and serious injuries on the nation’s roadways. Policymakers and partners can design and implement adaptive safety policies. They can also put forth policies that simultaneously build up Safe System–consistent practices while breaking down inconsistent practices. In addition, policymakers can advance policies that provide reliable and protective system redundancies for all road users. Indeed, policy provides the foundation from which to foster and maintain a truly Safe System. Chapter 3 focuses on Safe System–aligned planning.