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regarding existing requirements under the law or agency policies.

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An important Note on the Allowable Use of Treatments and Countermeasures 

All traffic control devices installed by an agency must be compliant with FHWA’s Manual on Traffic Control Devices 

(MUTCD). For certain treatments which are not MUTCD-compliant, an agency may request an experimentation waiver 

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website here (https://mutcd.fhwa.dot.gov/condexper.htm). 
Technical Report Documentation Page

1. Report No.

FHWA-SA-22-069 

2. Government Accession No. 3. Recipient’s Catalog No.

4. Title and Subtitle

Safe System Roadway Design Hierarchy: Engineering and 

Infrastructure-related Countermeasures to Effectively Reduce 

Roadway Fatalities and Serious Injuries

5. Report Date

January 2024

6. Performing Organization Code

7. Author(s)

Cory Hopwood, Kensington Little, Danena Gaines 

8. Performing Organization Report No.

9. Performing Organization Name and Address

Cambridge Systematics, Inc. Burgess& Niple, Inc. 

101 Station Landing, Suite 410 330 Rush Alley, Suite 700 

Medford, MA 02155 Columbus, OH 43215

10. Work Unit No. (TRAIS)

11. Contract or Grant No.

12. Sponsoring Agency Name and Address

U.S. Department of Transportation 

Federal Highway Administration Office of Safety 

1200 New Jersey Avenue, SE 

Washington, DC 20590 

13. Type of Report and Period Covered

14. Sponsoring Agency Code

FHWA

15. Supplementary Notes

This report was produced under the direction of Karen Scurry (FHWA Office of Safety). 

16. Abstract

Widespread implementation of safety countermeasures supports the Safe System Approach and 

can accelerate achieving local, State, and National safety goals. This document introduces the Safe 

System Roadway Design Hierarchy as a tool to characterize engineering and infrastructure-based 

countermeasures and strategies relative to their alignment with the goal of eliminating fatalities and 

serious injuries to support implementation of a Safe System Approach. The Safe System Roadway Design 

Hierarchy will also result in a greater understanding of Safe System principles and increased application 

of the Safe System Approach. 

17. Key Words

Safe System, Pedestrians, Bicyclists, Ped, 

Bike, Vision Zero, Road to Zero, Speed, Safety 

18. Distribution Statement

No restrictions.

19. Security Classif. (of this report)

Unclassified

20. Security Classif. (of this page)

Unclassified

21. No. of Pages

38

22. Price

Form DOT F 1700.7 (8-72) Reproduction of completed page authorized

SAFE SYSTEM ROADWAY 

DESIGN HIERARCHY 

The Safe System Roadway Design Hierarchy is a tool that characterizes 

engineering and infrastructure-based countermeasures and strategies 

relative to their alignment with the Safe System Approach (SSA), toward 

the goal of eliminating traffic-related fatalities and serious injuries. 

The purpose of the hierarchy is to help transportation agencies and 

practitioners identify and prioritize countermeasures and strategies 

when developing transportation projects. The Safe System Roadway 

Design Hierarchy will facilitate greater understanding and increased 

application of Safe System principles. FHWA developed the Safe System 

Roadway Design Hierarchy in response to a recommendation from the 

informational report on Integrating the Safe System Approach into the 

HSIP. The Safe System Roadway Design Hierarchy is emulated from 

the hierarchy of controls for workplace safety1 and previous work by 

Austroads,2 and is consistent with the Safe System Pyramid.3

The Safe System Roadway Design Hierarchy includes four tiers that are 

arranged from most to least aligned with the Safe System principles. 

Tiers 1 through 3 include solutions to remove potential roadway conflicts 

and separate vulnerable road users from traveling vehicles, with the goal 

of reducing crash kinetic energy if a crash does occur, whereas Tier 4 

countermeasures and strategies provide critical information to the road 

user so they can take appropriate action. In the Safe System Roadway 

Design Hierarchy, physical changes to the system are more effective than 

changes that rely on road users to make safe decisions. While the focus 

of this publication is on design improvements, agencies should consider 

all elements of the Safe System Approach when developing projects. 

This document introduces the Safe System Roadway Design Hierarchy 

and describes how various countermeasures and strategies align with 

each tier; explains how transportation agencies and practitioners can 

use the hierarchy; demonstrates how Complete Streets and FHWA’s 

Proven Safety Countermeasures support the SSA and align with the 

Safe System Roadway Design Hierarchy; and presents new or novel 

uses of countermeasures and strategies in each tier. Widespread 

implementation of safety countermeasures supports the SSA and 

can accelerate achieving local, State, and national safety goals. This 

document is illustrative, and is not inclusive of all strategies that could 

support implementation of the SSA but is intended to provide transportation agencies and practitioners with a new lens 

to consider how Safe System solutions can be implemented through example case studies and applications. 

The methods, solutions, and considerations presented in this document are current as of the time of this 

report. As we continue to integrate Safe System principles into our safety programs and advance infrastructure 

countermeasures and strategies that anticipate human error and accommodate human injury tolerances, new 

knowledge may result in future updates. Zero deaths and serious injuries on the Nation’s roadways is our goal. A 

Safe System is how we get there.

1

REMOVE SEVERE 

CONFLICTS

REDUCE VEHICLE 

SPEEDS

MANAGE CONFLICTS

IN TIME

INCREASE ATTENTIVENESS 

AND AWARENESS

TIER

1

TIER

2

TIER

3

TIER

4

SAFE SYSTEM

ROADWAY DESIGN 

HIERARCHY
DESCRIPTION OF SAFE SYSTEM ROADWAY DESIGN HIERARCHY TIERS 

TIER 1: REMOVE SEVERE CONFLICTS

Removing severe conflicts involves the elimination of specific high-risk conditions. This involves 

separating road users moving at different speeds or different directions in space to minimize conflicts 

with other road users. This tier includes strategies that remove conflicts such as intersection crossing 

conflicts, removing fixed objects along the roadside, or eliminating railway-highway crossings. Strategies 

in this tier may also include providing physical separation between motorized and non-motorized users 

to remove conflicts or providing varying degrees of buffered separation to reduce risk of collisions. 

These countermeasures support both the Safe Roads and Safe Road Users elements of the SSA.

TIER 2: REDUCE VEHICLE SPEEDS 

Implementing design features and speed management strategies to reduce vehicle speeds effectively 

reduces the kinetic energy involved in a crash should it occur. States and local jurisdictions should set 

appropriate speed limits to reduce the significant risks drivers impose on others—especially vulnerable 

road users—and on themselves. To achieve desired speeds, agencies often implement other speed 

management strategies concurrently with setting speed limits, such as self-enforcing roadways, traffic 

calming measures, and speed safety cameras. Self-enforcing roads involve the use of road and roadside 

design elements, such as lane narrowing, intersection channelization, and horizontal and vertical 

deflection, to elicit lower travel speeds of motor vehicles along the roadway. This also includes features 

for pedestrians and bicyclists, such as median islands, raised crosswalks, and buffered bicycle lanes. 

These countermeasures support the Safe Roads, Safe Speeds, and Safe Road Users elements of the SSA. 

2
TIER 3: MANAGE CONFLICTS IN TIME 

Managing conflicts in time assumes that users will need to occupy the same physical space on 

the roadway but creates a safer environment by separating the users in time using traffic control 

devices, such as traffic signals or hybrid beacons, to minimize vehicle conflicts. Providing discrete and 

alternating opportunities for users to navigate the roadway environment is not only a safety strategy, 

but also one that relates to user comfort and convenience, especially for non-motorized users. These 

solutions support the Safe Roads, Safe Speeds, and Safe Road Users elements of the SSA.

TIER 4: INCREASE ATTENTIVENESS AND AWARENESS

Increasing attentiveness and awareness involves alerting roadway users to certain types of conflicts so 

that appropriate action can be taken consistent with the SSA. Examples that fall into this category include 

crossing visibility enhancements, backplates with retroreflective borders, and rumble strips/stripes. These 

countermeasures support the Safe Roads, Safe Speeds, and Safe Road Users elements of the SSA. 

Transportation agencies and practitioners can use the Safe System Roadway Design 

Hierarchy as a framework for evaluating countermeasures or strategies based on their 

alignment with the Safe System principle that deaths and serious injuries are unacceptable. 

It is important to recognize that Safe System alignment is one of many factors that agencies 

or practitioners may consider when selecting possible countermeasures or strategies to 

address an identified safety problem. Other factors include but are not limited to community 

input, feasibility, extent of potential crash reduction, cost, project readiness and funding 

availability. The Safe System Roadway Design Hierarchy is intended to supplement other 

tools and information agencies use to identify, select, and prioritize countermeasures.

Source: FHWA.

3
HOW TO USE THE SAFE SYSTEM 

ROADWAY DESIGN HIERARCHY 

The Safe System Roadway Design Hierarchy is a project-based, site assessment tool. The 

application of countermeasures and strategies that align with the SSA is dependent on the 

context, classification, location, and users of the facility. An interstate freeway and a city 

street can both apply countermeasures and strategies that align with the SSA but applied 

in very different ways. The four tiers within the Safe System Roadway Design Hierarchy are 

general in nature and applicable to any scenario.

Source: Pedestrian Hybrid Beacon (PHB), FHWA.

When applying the hierarchy, agencies should consider countermeasures and strategies under Tier 1 first, as physical 

separation can permanently eliminate conflicts that lead to severe crashes. If that is not feasible, solutions from the 

subsequent tiers can then be selected, alone or in combination, to further enhance safety and move toward a Safe System. 

For example, the Pedestrian Hybrid Beacon is a countermeasure that cross-cuts among multiple tiers; specifically, it manages 

conflicts in time (Tier 3), increases attentiveness and awareness (Tier 4), and in combination with a raised crosswalk can 

reduce vehicular speeds (Tier 2). 

4
Often, agencies and practitioners will need to combine countermeasures and strategies from multiple tiers to be most 

effective. This approach reinforces the Safe System principle that redundancy is critical to reduce fatal and serious injury 

crashes. Complete Streets is a great example of applying a combination of countermeasures and strategies to support 

implementation of the SSA and improve safety for all users (further described on page 6). As another example, variable speed 

limits in combination with speed safety cameras on non-freeways at night can reduce speeding and related crashes. This is 

also an example of how agencies can use Proven Safety Countermeasures in a new or novel way. 

In other cases, an incremental approach to achieving a Safe System may be more feasible. If time or resources are a 

challenge, agencies can use one or more of the lower tier options as interim solutions until a permanent solution is in place. 

For example, an agency may install a centerline buffer area today, and then when funding is available in the future, they can 

implement a median barrier to remove the severe conflict. 

Some strategies within Tier 1 may involve providing physical space to separate conflicts between motorized and nonmotorized users. The degree of separation provided should be considered when assessing alignment with the SSA. An 

example is the varying degrees of buffered separation for a bicycle lane as shown in the figure below. Each design option 

shown has a differing amount of physical separation that can influence the risk of a collision with a motorized vehicle. 

The Safe System Roadway Design Hierarchy can also be used to prioritize in the planning phase through a Safe System lens. 

Agencies could integrate Safe System Roadway Design Hierarchy tiers into project prioritization rating criteria. For instance, 

agencies can assign each project points based on their alignment with SSA allowing those projects with greatest alignment to 

be prioritized for implementation. 

While the Safe System Roadway Design Hierarchy is a useful design strategy and countermeasure selection tool, agencies 

should continue to advance policy level strategies that support the SSA, including speed management and equity 

considerations for all road users. Transportation practitioners will make more rapid progress toward the goal of zero deaths 

and serious injuries on our Nation’s roadways by implementing effective speed management strategies at the agency level 

and addressing disparate traffic safety outcomes for underserved communities in all projects and programs.

5
COMPLETE STREETS

WHAT IS IT?

A Complete Street ensures the safe and adequate accommodation of all transportation system users, including pedestrians, 

bicyclists, public transportation users, children, older individuals, individuals with disabilities, motorists, and operators of transit 

and freight vehicles. As an implementation strategy of the SSA, Complete Streets focuses on creating safe, connected, and 

equitable networks that fit community needs and context. Two-thirds of the States have adopted Complete Street policies 

encompassing planning, design, construction, operations, and maintenance to improve network safety.

HOW DOES IT ALIGN WITH THE 

SAFE SYSTEM DESIGN HIERARCHY?

Complete Streets approaches vary depending on community context. Complete Streets may apply a wide range of 

integrated safety elements to develop a system that is safe for all users, such as sidewalks, bicycle lanes, curb extensions, 

gateway treatments, median refuge islands, road diets, and modified vehicle lanes. Complete Streets implementation may 

apply the Safe System Roadway Design Hierarchy to identify safety improvement projects. The figure below shows an 

example of a Complete Street using a road diet to reconfigure a four-lane highway, aligning the safety improvements within 

the Safe System Roadway Design Hierarchy. 

TIER 1: REMOVE SEVERE CONFLICTS

The roadway design provides separation in space to protect all 

roadway users. 

TIER 2: REDUCE VEHICLE SPEEDS

Self-enforcing road design and gateway treatments provide 

contextual encouragement for motorists to drive at safer speeds.

TIER 3: MANAGE CONFLICTS IN TIME

A Pedestrian Hybrid Beacon (PHB) can assist pedestrians 

crossing at the uncontrolled intersection.

TIER 4: INCREASE ATTENTIVENESS AND AWARENESS

Bicycle treatments and pedestrian signage make motorists aware 

of crossing cyclists and pedestrians.

Image source: Complete Streets Transformations, FHWA: Complete Streets Transformations (dot.gov).

6
COMPLETE STREETS CASE STUDY 

The Minnesota Department of Transportation (MnDOT) implemented a Complete Streets redesign and road diet along a 

section of Highway 24 in St. James, Minnesota. Highway 24 accommodates an average daily traffic of 5,000 to 7,000 vehicles, 

with heavy commercial vehicles representing ten percent of the traffic. MnDOT replaced traffic signals at two intersections 

with mini roundabouts, removed one travel lane, reduced lane widths, and replaced parallel parking with back-in angle 

parking. In addition, the project added improved sidewalks, crosswalks, and curb extensions to make walking and biking more 

comfortable. These improvements reduced vehicle travel speeds and improved visibility of people walking and biking. 

To increase public familiarity of the redesign, MnDOT conducted public events and targeted engagement to reach senior 

and Latino communities in the area, such as distributing project briefings in Spanish. In addition, the project team conducted 

driving simulations with freight trucks and school buses to demonstrate how roundabouts do not limit access for large 

vehicles. Residents had the opportunity to learn about mini-roundabouts and practice back-angle parking at public events. The 

corridor redesign reduced crossing distances for people walking and biking, calmed traffic, and improved visibility.4

Source: Complete Streets Case Studies (Highway 24 in St. James), Minnesota Department 

of Transportation: https://www.dot.state.mn.us/complete-streets/examples.html.

7
PROVEN SAFETY COUNTERMEASURES (PSC) 

Many agencies already implement one or more of FHWA’s Proven Safety Countermeasures (PSC) that support a SSA, such as 

road diets, rectangular rapid flashing beacons, and longitudinal rumble strips. The table below shows how the PSCs align with 

each tier in the Safe System Roadway Design Hierarchy. Some PSCs align with one tier, whereas other PSCs support multiple 

tiers. For example, roundabouts align with both Tier 1 (Remove Severe Conflicts) and Tier 2 (Reduce Vehicle Speeds); leading 

pedestrian intervals aligns with Tier 3 (Manage Conflicts in Time); and variable speed limits align with both Tier 2 (Reduce 

Vehicle Speeds) and Tier 4 (Increase Attentiveness and Awareness). 

Proven Safety Countermeasure

Tier 1 

Remove Severe 

Conflicts

Tier 2

Reduce Vehicle 

Speeds 

Tier 3

Manage 

Conflicts in Time 

Tier 4 

Increase Attentiveness 

and Awareness

Speed Management

Appropriate Speed Limits 

for All Road Users

Speed Safety Cameras

Variable Speed Limits

Pedestrian/Bicyclist 

Bicycle Lanes

Crosswalk Visibility 

Enhancements

Leading Pedestrian 

Interval

Medians and Pedestrian 

Refuge Islands

Pedestrian Hybrid 

Beacons

Rectangular Flashing 

Beacons (RRFB)

Road Diets

Walkways

Roadway Departure 

Enhanced Delineation for 

Horizontal Curves

Longitudinal Rumble 

Strips and Stripes

Median Barriers

8
Proven Safety Countermeasure

Tier 1 

Remove Severe 

Conflicts

Tier 2

Reduce Vehicle 

Speeds 

Tier 3

Manage 

Conflicts in Time 

Tier 4 

Increase Attentiveness 

and Awareness

Roadway Departure (continued)

Roadside Design 

Improvements at Curves

SafetyEdgeSM

Wider Edge Lines

Intersections 

Backplates with 

Reflective Borders

Corridor Access 

Management

Dedicated Left and 

Right Turn Lanes at 

Intersections

Reduced Left Turn 

Conflict Intersections

Roundabouts

Systemic Application 

of Multiple Low-Cost 

Countermeasures at StopControlled Intersections

Yellow Change Intervals

Crosscutting 

Lighting

Local Road 

Safety Plans

Pavement Friction 

Management

Road Safety Audit

9
CHARACTERIZING SAFE SYSTEM SOLUTIONS

The following section characterizes Safe System countermeasures and strategies based on their alignment with the Safe 

System Roadway Design Hierarchy. Multiple countermeasures or strategies are presented for each tier, including a description 

of what the countermeasure is, how it aligns with the SSA, potential benefits and risk factors the countermeasure may address, 

and an example of the countermeasure in practice. The countermeasures and strategies may be an existing PSC, an existing 

PSC implemented in a different way, or a new and emerging countermeasure or strategy. Each tier section concludes with a 

list of resources to support the implementation of countermeasures and strategies. 

TIER 1:

REMOVE SEVERE CONFLICTS

Removing severe conflicts involves the elimination of specific high-risk conditions. These countermeasures separate road 

users moving at different speeds or different directions in space to minimize their conflicts with other road users. 

ROUNDABOUTS

WHAT IS IT?

Roundabouts are intersections with 

a circular configuration that use 

channelized, curved approaches to 

reduce vehicle speeds and minimize 

conflict points. Roundabouts direct the 

flow of traffic counterclockwise around 

a central island to efficiently move all 

road users through the intersection 

while calming traffic. 

Roundabouts are highly adaptable, and 

can range from “mini” roundabouts 

to multilane roundabouts, and can be 

used in both high speed rural and low 

speed urban contexts, and even for 

interchanges. An emerging form of the 

roundabout is known as a “turbo”, which 

is a multilane design with additional and 

more robust channelization. 

HOW DOES IT ALIGN 

WITH THE SSA?

Roundabouts eliminate intersection 

crossing conflict points, slow down vehicle speeds, and manipulate crash angles to reduce the kinetic energy involved in 

a vehicle crash. In addition, roundabouts limit pedestrian exposure to oncoming traffic by allowing pedestrians to cross 

one direction of traffic at a time and may include pedestrian refuge areas. 

Source: Turbo Roundabout (Jacksonville, Florida), FHWA.

10
WHAT ARE THE BENEFITS OF ROUNDABOUTS?

Roundabouts are safer alternatives to traditional intersections and can 

reduce injury and fatal crashes by 78 to 82 percent when replacing 

traffic signals or stop signs in the United States.5 Converting signalized 

intersections into a two lane roundabout at 16 sites in 10 States 

indicated a 71 percent reduction in fatal and serious injury crashes when 

applied in urban or suburban areas with a minimum of 5,300 Annual 

Average Daily Traffic (AADT) and maximum of 52,000 AADT, and speed 

setting of a minimum of 15mph and maximum of 35mph.6

Based on studies in Europe, roundabouts may also reduce pedestrian 

crashes by 75 percent.7

 In Belgium, traditional signalized intersections were replaced by roundabouts with separated bicycle 

pathways, reducing vehicle/bicycle fatal and serious injury crashes by 44 percent.8

THIS COUNTERMEASURE IN PRACTICE

The intersection of Frankford Avenue, Trenton Avenue, and York Street in Philadelphia, Pennsylvania implemented 

a low-cost compact roundabout to reduce vehicle speeds and provide accommodations for pedestrians, trucks, and 

buses. The roundabout design included ADA compliant curb ramps and sidewalks, splitter islands, enhanced LED 

lighting, signage, pavement markings, truck aprons, and a main central island designed to let large trucks traverse 

the island if needed.

ROUNDABOUTS MAY ADDRESS 

THE FOLLOWING RISK FACTORS: 

Lack of Pedestrian/Cyclist Space 

Separation, Undivided Roadway, 

Permissive Left Turn Conflicts, Intersection 

Crossing Conflict, and High/Excessive 

Vehicle Speeds.

Source: Compact Roundabout (Washentaw County, Michigan), FHWA. 

11

TIER 1: REMOVE SEVERE CONFLICTS
DIVERGING DIAMOND INTERCHANGE

WHAT IS IT?

A Diverging Diamond Interchange (DDI) is an innovative design solution 

that improves safety and mobility for motorists, pedestrians, and bicyclists 

by creating intuitive crossovers that transition traffic from the right side of 

the road and then back again. This design eliminates the need for left turns

across opposing traffic and simplifies pedestrian crossing movements.

DDIs are best utilized in locations with high volumes of left turns, 

unbalanced crossroad traffic volumes, and where there is a need for 

additional capacity without widening the roadway. DDI’s typically have 

improved operational efficiency and fewer conflict points in comparison to 

conventional diamond interchanges. 

HOW DOES IT ALIGN WITH THE SSA?

DDIs reduce potential areas of conflict for those biking, walking, and driving.

This design may provide bicycle lanes located to the right of traffic to protect

people biking, and may be paired with roadway signs or pavement markings

to support safe travel for all roadway users.

WHAT ARE THE BENEFITS OF 

DIVERGING DIAMOND INTERCHANGES?

Compared to the conventional diamond interchange, which is 

the most common form in the United States, the DDI reduces 

vehicle-to-vehicle conflict points by nearly 50 percent and 

eliminates most severe crash types.9 Converting traditional 

diamond interchanges to DDIs at 80 locations in 24 States 

resulted in a 44 percent reduction in fatal and serious injury 

crashes when applied in urban or suburban areas with a 

minimum of 1,295 AADT and maximum of 76,100 AADT on 

arterial roadways.10

THIS COUNTERMEASURE IN PRACTICE 

The Minnesota Department of Transportation converted two signalized diamond interchanges, with a minimum 

of 28,000 AADT to a maximum of 40,000 AADT on major roads and minimum of 3,000 AADT to a maximum of 

18,000 AADT on minor roads, to DDIs. According to a before and after safety evaluation conducted between 

2006 to 2015, the signalized intersections resulted in an estimated 304 crashes, whereas 37 crashes were 

recorded after the DDI redesign.11

DDIS MAY ADDRESS THE

FOLLOWING RISK FACTORS: 

Permissive Left Turn Conflicts, Intersection

Crossing Conflict, and Lack of Pedestrian/

Cyclists Space Separation.

Source: Getty Images.

12
SEPARATED BIKE LANES

WHAT IS IT?

Separated bike lanes, also known as protected bicycle lanes, 

segregate bicyclists from motor vehicles by incorporating a buffer 

space and vertical element between vehicle travel lanes and the 

bicycle lane.

HOW DOES IT ALIGN 

WITH THE SSA?

Separated bike lanes provide a dedicated pathway for cyclists, 

which reduces the distance and time in which cyclists are 

exposed to conflicts with motorists. 

WHAT ARE THE BENEFITS OF 

SEPARATED BIKE LANES?

Separated bike lanes improve visibility between people biking and 

driving, increase the degree of comfort and safety for all bicyclists 

regardless of their abilities, and support a network of predictable 

movements across all road users. Converting a traditional bicycle 

lane to a separated bike lane using vertical flexible delineator 

posts resulted in a 50 percent decrease in fatal and serious injury 

crashes when applied to urban areas in Cambridge (MA), San 

Francisco (CA), and Seattle (WA).12 

THIS COUNTERMEASURE IN PRACTICE

The New York City Department of Transportation implemented separated bicycle lanes to separate passing motor 

vehicle traffic by a parking lane and buffer. This design used striping, markings, signage, vertical elements, and 

intersection treatments to achieve a 75 percent risk reduction with respect to bicyclist serious injuries.13

Source: Raised Separated Bike Lane (Fremont, California), FHWA.

Source: Making Safer Streets, New York City Department of Transportation: dot-making-safer-streets.pdf (nacto.org).

SEPARATED BIKE LANES MAY ADDRESS 

THE FOLLOWING RISK FACTORS: 

Lack of Pedestrian/Cyclists Space Separation 

and Undivided Roadway.

13

TIER 1: REMOVE SEVERE CONFLICTS
PROTECTED INTERSECTION 

WHAT IS IT?

Protected intersections use a setback or offset design to reduce conflict points and increase visibility between drivers and 

those bicycling or walking. Protected intersection features may include pedestrian refuge islands, bicycle queuing areas, 

corner islands, and intersection crossing markings to protect all road users and enhance system predictability. Implementation 

of a protected intersection should consider a variety of factors, such as accessibility needs and trip purposes, to develop 

comprehensive solutions that align with the surrounding roadway context. 

HOW DOES IT ALIGN WITH THE SAFE SYSTEM APPROACH?

Protected intersections reduce certain conflicts and enhance the physical separation between people walking and biking 

and vehicles. Protected intersection features may reduce the speed of vehicle turning movements, thus reducing the kinetic 

energy if a crash does occur. Therefore, protected intersection features can also be considered a Tier 2 countermeasure. 

Intersection enhancement projects are opportunities to provide safe, more equitable, and accessible facilities for all road users 

regardless of age or abilities. 

WHAT ARE THE BENEFITS OF 

PROTECTED INTERSECTION FEATURES?

Protected intersection features improve crossing visibility 

and sight distance to reduce potential conflicts. For example, 

medians with marked cross walks can reduce pedestrian 

crashes by 26 percent, and pedestrian refuge 

islands can reduce pedestrian crashes by 56 percent.14 

THIS COUNTERMEASURE IN PRACTICE

The New York City Department of Transportation implemented various protected intersection features including 

pedestrian ramps, safety islands, and bicycle facilities along Columbus Ave, W 96th St to W 77th St, resulting in a 25 

percent reduction in injury crashes.15

Source: Improving Intersections for Pedestrians and Bicyclists, FHWA: 

https://highways.dot.gov/sites/fhwa.dot.gov/files/2022-06/fhwasa22041.pdf

PROTECTED INTERSECTION FEATURES MAY 

ADDRESS THE FOLLOWING RISK FACTORS: 

Lack of Pedestrian/Cyclists Space Separation, 

Obstructed Sight Distance, and Intersection 

Crossing Conflict.

The diagram shows how:

1) bike lane transitions; 

2) protected intersection 

features; and 3) crossing 

islands can improve traditional 

signalized intersections.

14
CABLE MEDIAN BARRIERS 

WHAT IS IT?

As opposed to rigid concrete barriers, cable barriers are mode from 

steel cables mounted on weak steel posts that remain flexible. These 

barriers absorb energy from a crash by capturing or redirecting the 

vehicle. 

HOW DOES IT ALIGN WITH THE SSA?

Cable barriers can be used as a strategy to reduce the number of 

cross-median crashes or be implemented as a flexible guardrail to 

reduce crash severity. This countermeasure reduces impact forces 

to the motor vehicle and in turn reduces impacts to the human body 

during a crash. 

WHAT ARE THE BENEFITS OF CABLE BARRIERS?

Median barriers are typically implemented on high-speed, fully 

controlled access roadways; however, the flexibility and design of 

cable barriers allows for a wide variety of unique applications to 

support the SSA. For example, installing wire guardrails between 

lanes of opposing traffic resulted in a 26 percent decrease in 

fatal and serious injury crashes when applied on principle arterial 

roadways with three travel lanes.16 

THIS COUNTERMEASURE IN PRACTICE

The Oregon Department of Transportation implemented cable barriers along narrow medians (less than 8 feet wide) 

to reduce crossover crashes on Mount Hood Highway (US-26) resulting in a 29 percent reduction in fatal and serious 

injury crash rates.17

Source: Cable Barrier (Oregon Mount Hood Highway 

US-26), K. Burns and Katherine E Bell: https://www.

semanticscholar.org/paper/Performance-Evaluation-ofa-Cable-Median-Barrier-on-Burns-Bell/3b556bdc0762

981e9f88612a1247d0d9e91f5591

Source: Cable Barrier (1-70 near Friendship, Maryland), Wikipedia Commons: 

https://commons.wikimedia.org/wiki/File:2008_03_28_-_I70_Cable_Barrier.JPG.

CABLE BARRIERS MAY ADDRESS THE 

FOLLOWING RISK FACTORS: 

Undivided Roadway and Vertical and 

Horizontal Curvature.

15

TIER 1: REMOVE SEVERE CONFLICTS
SUPER 2 DESIGN

WHAT IS IT?

A Super 2 design adds a periodic passing lane to a two-lane rural 

highway to allow for the passing of slower vehicles. A Super 2 design 

may be introduced on an existing two-lane roadway with a significant 

amount of slow-moving traffic, limited sight distance for passing, or 

when the existing traffic volume has exceeded the two-lane highway 

capacity, creating the need for vehicles to pass on a more frequent 

basis. 

HOW DOES IT ALIGN WITH THE SSA?

The Super 2 highway network design reduces conflict points by 

providing a designated travel lane for motor vehicles to pass slowermoving vehicles. This design reduces risky driver behaviors by 

improving visibility and protecting drivers from potential severe headon crashes. 

WHAT ARE THE BENEFITS OF SUPER 2 DESIGN?

The Super 2 design has been adopted as a safety strategy in Texas and Kentucky. 

Super 2 designs have also been implemented in countries such as Spain, Ireland, 

New Zealand, Germany, Finland, and Sweden. In Sweden, the Super 2 design 

resulted in a 55 percent reduction in fatal and serious injury crashes.18

THIS COUNTERMEASURE IN PRACTICE

The Texas Department of Transportation analyzed the operational and safety benefits of the Super 2 design on 

two-lane roads with traffic volumes between 5,000 and 15,000 vehicles per day, finding that the design resulted 

in a 35 percent reduction in expected non-intersection injury crashes and a 42 percent reduction for segments 

with intersections.19

Source: Super 2 Design, Texas A&M Institute (TTI): 

https://tti.tamu.edu/researcher/two-decades-of-super-2-researchand-implementation-for-txdot-continues-to-produce-benefits/.

A SUPER 2 DESIGN MAY 

ADDRESS THE FOLLOWING 

RISK FACTORS: 

Obstructed Sight Distance, Vertical 

and Horizontal Curvature, and 

High/Excessive Vehicle Speeds.

Source: Iowa Design Manual. 16
CENTERLINE BUFFER AREAS

WHAT IS IT?

Centerline buffer areas provides additional space between the 

two solid centerline markings, creating further separation between 

opposing directions of traffic.

HOW DOES IT ALIGN WITH THE 

SAFE SYSTEM APPROACH?

Centerline buffer areas reduce vehicle conflict points and potential 

head-on crashes through roadway design. 

WHAT ARE THE BENEFITS OF 

CENTERLINE BUFFER AREAS?

Centerline buffer areas were evaluated based on their 

effectiveness to reduce head-on crashes on rural two-lane 

roadways. Implementing a two-foot buffer area reduced crashes by 

35 percent; a four-foot buffer area reduced crashes by 64 percent; 

and a 10-foot buffer area reduced crashes by 90 percent.20

THIS COUNTERMEASURE IN PRACTICE

The Minnesota Department of Transportation conducted a road audit on Highway 14, finding that 70 percent of 

fatal and serious injury crashes were a result of a vehicle crossing the centerline. The Minnesota Department of 

Transportation then converted the highway into a no-passing zone, implemented an eight-foot centerline buffer area 

using double yellow striping, installed rumble strips on each side, and installed delineators every 50 feet within the 

buffer area to reinforce the presence of the no-passing zone. These improvements reduced fatal and serious injury 

crashes by 100 percent and cross centerline crashes by almost 50 percent.21

RESOURCES: 

Additional information to support Tier 1 – Remove Severe Conflicts:

CENTERLINE BUFFER AREAS MAY ADDRESS 

THE FOLLOWING RISK FACTOR: 

Undivided Roadway.

Bikeway Selection Guide

Separated Bike Lane Planning and Design Guide

State Best Practice Policy for Medians 

Intersections

Super 2 Research TxDOT

Primer on Safe System Approach for 

Pedestrians and Bicyclists 

Source: Centerline Buffer Area with yellow strips 

and centerline rumble strips (Highway 14), Minnesota 

Department of Transportation:

17

TIER 1: REMOVE SEVERE CONFLICTS
TIER 2: 

REDUCE VEHICLE SPEEDS 

Implementing design features and speed management strategies to reduce vehicle 

speeds effectively reduces the kinetic energy involved in a crash should it occur. States 

and local jurisdictions should set appropriate speed limits to reduce the significant risks 

drivers impose on others—especially vulnerable road users—and on themselves.

SELF-ENFORCING ROADS

WHAT IS IT?

A self-enforcing or self-explaining roadway is planned, designed, and operated to offer 

contextual encouragement for motorists to drive at safer speeds in alignment with the 

roadway purpose and adjacent land uses. These roadways are generally guided by six 

concepts to encourage effective and safe decision making to reduce severe crashes. 

These concepts include applying the speed feedback loop process; using the inferred 

design speed approach; applying operating speed models; utilizing existing geometric 

design criteria; using a combination of signs and pavement marking; and setting rational 

speed limits. 

Self-enforcing roads may also integrate mechanisms such as Transportation Systems 

Management and Operations (TSMO) strategies to develop a proactive and predictive 

transportation network, and Intelligent Transportation Systems (ITS) to improve mobility 

and safety through technology advancements. 

HOW DOES IT ALIGN WITH THE SSA?

Self-enforcing roads support the Safe System principle that humans 

make mistakes by communicating contextual clues and driver 

expectations through design and operations, thus resulting in fewer 

human errors. These roadways encourage drivers to reduce travel 

speeds, thereby limiting the kinetic energy associated with high-speed 

traffic crashes, and simultaneously improving roadway safety for all 

users. Self-enforcing roads may be supplemented with other safety 

countermeasures such as roundabouts, pedestrian refuge islands, and 

raised crosswalks to support a Safe System. 

WHAT ARE THE BENEFITS OF SELF-ENFORCING 

OR SELF-EXPLAINING ROADS?

An analysis on speed management research conducted on New Zealand roads showed that speed change thresholds and 

speed treatments (such as reducing roadway widths and the number of lanes and the installation of rumble stripes, landscaping, 

speed humps, side barriers, center medians, centerline treatments, and signage) reduced vehicle speeds by 27 percent and 

reduced the number of serious injury crashes by 15 percent.22

THIS COUNTERMEASURE IN PRACTICE

The City of Golden, Colorado rebuilt the South Golden Road corridor using a self-enforcing design to reduce vehicle 

speeds, improve vulnerable road user safety, and develop a pedestrian and bicycle friendly environment. The design 

included replacing traffic signals with roundabouts, narrowing roads using center medians, and restricting left turns to 

improve access to businesses and protect vulnerable road users. The enhancements reduced total crashes per month 

by 36 percent, injuries per month by 97 percent, and bike-related crashes from 78 crashes recorded over the five years 

before the improvements to just four crashes over the 3.5 years after the corridor was completed.23

Source: South Golden Road before and after 

improvements (City of Golden, Colorado), Dan 

Hartman: https://highways.dot.gov/safety/

speed-management/noteworthy-practicebooklet-speed-management/case-study-2-

noteworthy-speed.

SELF-ENFORCING ROADS MAY ADDRESS 

THE FOLLOWING RISK FACTORS: 

Obstructed Sight Distance, High/Excessive 

Vehicle Speeds, Vertical and Horizontal 

Curvature, Crossing Conflict Intersections, 

Driveway Density, Undivided Roadway, and 

Lack of Pedestrian/Cyclist Space Separation.

18
RAISED CROSSWALKS

WHAT IS IT?

Raised crosswalks are crosswalks that are typically between 

three and six inches above street level, providing vertical 

delineation to increase visibility of crossing pedestrians. 

HOW DOES IT ALIGN WITH THE SSA?

Raised crosswalks function similarly to speed humps and are 

effective at reducing motor vehicle speeds while simultaneously 

encouraging drivers to yield to pedestrians in the crosswalk. 

Raised crosswalks may also be combined with other pedestrian 

crossing countermeasures such as overhead flashing beacons to 

increase pedestrian visibility and allow pedestrians to establish their 

presence on the roadway.

WHAT ARE THE BENEFITS OF 

RAISED CROSSWALKS?

Raised crosswalks may reduce pedestrian crashes by 45 

percent.24 For example, when applied on local two-lane 

roadways in urban and suburban areas, raised crosswalks 

reduced fatal and serious injury crashes by 46 percent.25

THIS COUNTERMEASURE IN PRACTICE

Raised crosswalks among other traffic calming improvements were constructed in Cambridge, Massachusetts 

to improve safety and reduce motor vehicle speeds. For the raised crosswalks, the City used concrete pavers to 

replicate the look and feel of brick, providing a color contrast to increase effectiveness. Before the improvements, the 

85th percentile speed on Granite Street was 28 mph. After the improvements, the speed was reduced to 24 mph.26

Source: Raised Crosswalk, City of Cambridge, Massachusetts: 

https://statics.teams.cdn.office.net/

evergreen-assets/safelinks/1/atp-safelinks.html.

Source: Improving Intersections for Pedestrians and Bicyclists, FHWA: 

https://highways.dot.gov/sites/fhwa.dot.gov/files/2022-06/fhwasa22041.pdf.

RAISED CROSSWALKS MAY ADDRESS THE 

FOLLOWING RISK FACTORS: 

Lack of Pedestrian/Cyclist Space Separation, 

Obstructed Sight Distance, Intersection Crossing 

Conflict, and High/Excessive Vehicle Speeds.

The diagram shows how: 1) 

crossing islands; 2) signalized 

crossings; and 3) raised bike and 

pedestrian crossings can improve 

displaced left turn intersections.

19

TIER 2: REDUCE VEHICLE SPEEDS
GATEWAYS 

WHAT IS IT?

Gateways are physical features or geometric landmarks 

that are part of a wayfinding system and send a clear 

message to motorists that the roadway network context 

is changing. These features may include signage, 

medians, archways, roundabouts, landscaping, brick 

paving, decorative fencing, and more. Gateways are 

often located at key entrance points to neighborhoods 

or downtowns. 

HOW DOES IT ALIGN WITH THE SSA?

Gateways are a form of traffic calming treatments, which 

aim to reduce travel speeds by creating an expectation 

for motorists to drive more slowly and to increase 

awareness of their surroundings.

WHAT ARE THE BENEFITS OF GATEWAYS?

Gateways alert drivers that they are entering an area 

that may have increased bicycle or pedestrian activity 

or changing roadway configurations, increasing their 

awareness of all roadway users. Constructing gateway 

monuments, roadside structures, and wayfinding signage 

resulted in a 32 percent reduction in fatal and serious injury 

crashes when applied on State-owned roadways with a 

minimum of 3,300 AADT and maximum of 34,000 AADT.27

THIS COUNTERMEASURE IN PRACTICE

The Michigan Department of Transportation developed a highly effective pedestrian gateway treatment to encourage 

drivers to yield to pedestrians in crosswalks. The pedestrian gateway treatment features RI-6 yield signs at both 

ends of the crosswalks and a flexible delineator post or yield sign in between travel lanes. According to the Michigan 

Department of Transportation, this treatment is appropriate for intersections and midblock crosswalks with speed limits 

of 35 mph or less. The treatment may be used on a variety of roadway configurations including one and two way travel 

lanes, with or without pedestrian refuge areas, and with or without bike lanes. According to two studies that measured 

effectiveness, the pedestrian crossing configuration resulted in a 70 to 90 percent vehicle speed compliance rate on 

roads with posted speeds of 30 mph or lower with up to 25,000 vehicle ADT.28

Source: Overhead reduced speed reduction sign leading up to the 

Village of Chatham gateway sign (Village of Chatham, Pennsylvania), 

Google Street View.

GATEWAYS MAY ADDRESS THE 

FOLLOWING RISK FACTORS: 

High/Excessive Vehicle Speeds, Proximity to Schools, 

and Lack of Pedestrian/Cyclist Space.

20
SPEED HUMP/BUMP

WHAT IS IT?

Speed humps, often displayed as speed bumps on signage, 

are vertical ramps that aim to reduce vehicle speeds by 15 

to 20 mph on one-way or two-way roads. Speed humps 

are commonly two to four inches high and 12 to 14 feet 

wide, with a ramp length of three to six feet depending on 

the target speed of the roadway. As recommended by the 

Manual of Uniform Traffic Control Devices (MUTCD-W17-1), 

speed humps may be accompanied by a warning sign of 

the upcoming roadway design feature. 

HOW DOES IT ALIGN WITH THE SSA?

Speed humps are a form of traffic calming treatments which force drivers 

to travel at reduced, and often safer, speeds.

WHAT ARE THE BENEFITS OF 

SPEED HUMPS/BUMPS?

Speed humps may be implemented as a strategy to reduce travel speeds at prioritized 

locations with high volumes of vulnerable road users (e.g., near schools), or implemented 

consecutively to calm traffic across longer portions of the roadway network. For example, 

installing speed humps on local 2 lane roadways in both urban and suburban areas 

resulted in a 50 percent decrease in fatal and serious injury crashes.29

THIS COUNTERMEASURE IN PRACTICE

The New York City Department of Transportation designates Neighborhood Slow Zones to reduce crash occurrence and 

severity. The Neighborhood Slow Zone program integrated gateway signage, 20 mph pavement markings, and speed 

humps to encourage motorists to drive slowly. These improvements reduced vehicle speeds by 10 to 25 percent, resulting 

in a 10 percent overall reduction in injury crashes and a 27 percent reduction in vehicle injury crashes.30

RESOURCES: 

Additional information to support Tier 2 – Reduce Vehicle Speeds:

SPEED HUMPS 

MAY ADDRESS THE 

FOLLOWING RISK FACTOR: 

High/Excessive Vehicle 

Speeds.

Source: Traffic Calming Speed Hump, 

Robert Drudi (Creative Commons License). 

Evaluation of Lane Reduction “Road Diet” Measures 

and their Effects on Crashes and Injuries

Pedestrian Gateway Treatment

ITE Traffic Calming Library

Synthesis of Safety Research Related 

to Speed and Speed Management 

Complete Streets Transformations

Complete Streets Best Policy and 

Implementation Practices

21

TIER 2: REDUCE VEHICLE SPEEDS
TIER 3: 

MANAGE CONFLICTS IN TIME 

Managing conflicts in time assumes that users will need to occupy the same physical space on the roadway and creates a 

safer environment by separating the users in time using traffic control devices, such as traffic signals or hybrid beacons, to 

minimize vehicle conflicts. Providing discrete and alternating opportunities for users to navigate the roadway environment is 

not only a safety strategy, but also one that relates to user comfort and convenience, especially for non-motorized users.

LEFT TURN PHASING

WHAT IS IT?

Protected left turn phasing provides a green or yellow 

arrow for 

left-turning vehicles while stopping both on-coming 

traffic and parallel pedestrian crossings. 

HOW DOES IT ALIGN 

WITH THE SSA?

Protected left turn phasing eliminates conflicts 

between cross traffic, left-turning vehicles, and 

pedestrians using the parallel crosswalk. This strategy 

may also be enhanced with leading pedestrian 

intervals to clear pedestrians through the crossings 

and reduce pedestrian and motor vehicle conflict points. 

WHAT ARE THE BENEFITS OF 

LEFT TURN PHASING?

Changing permissive left-turn phasing to protected left-turn phasing 

in Utah resulted in an 87 percent reduction in fatal and serious injury 

traffic crashes.31

THIS COUNTERMEASURE IN PRACTICE

The cities of Detroit and Grand Rapids, Michigan, upgraded permissive left-turn signals to protected left turn phasing 

at three locations. These improvements reduced total left-turn head-on crashes at the selected intersections by 

84 percent, injury crashes by 59 percent, and total crashes by 32 percent per year.32

Source: Cambridge Systematics, Inc.

PROTECTED LEFT TURN PHASING MAY 

ADDRESS THE FOLLOWING RISK FACTORS: 

Permissive Left Turn Conflicts and Lack of 

Pedestrian/Cyclists Time Separation.

22
COORDINATED SIGNAL TIMING 

WHAT IS IT?

Coordinated signal timing uses synchronized traffic movements to 

create an uninterrupted flow of traffic along a corridor with frequent 

intersections. Coordinated signal timing may set desired progression 

speeds to fit the roadway’s surrounding context through platooning. It 

may also be applied in areas with high pedestrian and bicyclist volumes 

to achieve desired operating speeds and to prioritize pedestrian and 

bicyclists travel. 

HOW DOES IT ALIGN WITH THE SSA?

Coordinated signal timing reduces potential conflicts associated with 

interrupted traffic flow for all roadway users, including motorists, transit 

vehicle operators and passengers, bicyclists, and pedestrians. 

WHAT ARE THE BENEFITS OF 

COORDINATED SIGNAL TIMING?

Coordinated signal timing may reduce the number of stops along a 

corridor and provide a continuous flow of traffic at the target speed. For 

example, a 12 intersection corridor on Glades Road in Boca Raton (FL) 

served as a case study to explore how optimized signal timing could 

address safety and efficiency, resulting in a 7 percent reduction in traffic 

conflicts when compared to the initial signal timings.33

THIS COUNTERMEASURE IN PRACTICE

As part of Vision Zero, the New York City Department of Transportation implemented the Arterial Slow Zone Program 

to improve corridor mobility and prevent traffic fatalities. The program utilizes a combination of tools, including setting 

a lower speed limit, using distinctive blue-and-white roadway signage to make drivers aware of the changing roadway 

context, and implementing temporary traffic speed enforcement boards at key locations along the corridors to warn 

motorists of the new speed limit. The Arterial Slow Zone Program retimes traffic signals to ensure consistency with the 

new speed limit, discourage speeding, and maintain an uninterrupted traffic flow.34

Source: Urban Street Design Guide, NACTO.

COORDINATED SIGNAL TIMING 

MAY ADDRESS THE FOLLOWING 

RISK FACTOR: 

High/Excessive Vehicle Speeds.

23

TIER 3: MANAGE CONFLICTS IN TIME
PEDESTRIAN SCRAMBLE 

WHAT IS IT?

A pedestrian scramble, also known as a Barnes dance 

or an all-walk phase, is an exclusive signal phase that 

allows pedestrians to cross an intersection in any 

direction. Vehicles on all approaches are stopped 

during the pedestrian scramble. Pedestrian scrambles 

may be beneficial in locations where other crossing 

improvement treatments are prohibited by cost or 

right-of-way concerns. 

HOW DOES IT ALIGN WITH THE SSA?

A pedestrian scramble removes points of conflict 

between turning vehicles and crossing pedestrians. 

This reduces pedestrians’ exposure to conflict and 

overall crossing time while increasing their visibility in 

the roadway. Pedestrian scrambles are often paired 

with other pedestrian crossing improvements such as 

curb extensions, high-visibility crosswalk markings, and 

“No Turn on Red” restrictions and signage. 

WHAT ARE THE BENEFITS OF 

PEDESTRIAN SCRAMBLES?

A pedestrian scramble gives pedestrians priority in the 

intersection while removing conflicts with turning vehicles. 

Implementing a pedestrian scramble on urban roadways in New 

York City resulted in a 51 percent reduction in vehicle/pedestrian 

fatal and serious injuries crashes.35

THIS COUNTERMEASURE IN PRACTICE

A pedestrian scramble was implemented at the intersection of 8th and Webster Streets in the Chinatown 

neighborhood in Oakland, California. Before the pedestrian scramble was implemented, observations of the 

intersection revealed vehicle delays and vehicle encroachment in the crosswalk, resulting in a total of 77 conflicts. The 

implementation process included public outreach efforts such as distributing multilingual brochures and conducting 

workshops to educate the community on the new intersection design. Following implementation, observers recorded 

a total of 35 conflicts, noting a significant decrease in pedestrian-vehicle conflicts.36 

Source: Pedestrian Scramble, Los Angeles Department of Transportation.

PEDESTRIAN SCRAMBLE MAY ADDRESS 

THE FOLLOWING RISK FACTORS: 

Lack of Pedestrian/Cyclists Time Separation, 

Skewed Geometry, Intersection Density, and 

Intersection Crossing Conflict.

24
EMERGENCY VEHICLE PREEMPTION

WHAT IS IT?

An emergency vehicle preemption (EVP) system uses ITS 

technology at signalized intersections to provide a green 

interval for an emergency vehicle approaching an intersection, 

and a red interval on all conflicting approaches. This allows 

emergency vehicles to safely travel through areas with levels of 

high congestion.

HOW DOES IT ALIGN WITH THE SSA?

EVP systems align with the Post-Crash Care element of the 

SSA by separating emergency vehicles in time from traveling 

motorists. EVP systems may improve incident response times 

by prioritizing the emergency vehicle through an intersection. 

Similar to yellow change intervals, EVPs also reduce potential 

conflict points and reduce the likelihood of crashes. 

WHAT ARE THE BENEFITS OF EVP?

EVPs increase overall safety at intersections by improving 

driver awareness of approaching emergency vehicles. EVPs also 

provide separation in time to facilitate the safe passing of 

emergency vehicles through roadway traffic. This system may 

reduce the risk of emergency vehicle crashes with motorists 

while also improving incident response times, creating a safe 

and integrated transportation network. 

THIS COUNTERMEASURE IN PRACTICE

An EVP system in the City of Plano, Texas reduced the number of emergency vehicles crashes from an average of 2.3 

intersection crashes per year to less than one intersection crash every five years.37

RESOURCES

Additional information to achieve Tier 3 – Manage Conflicts in Time: 

Leading Pedestrian Interval

Urban Street Design Guide

Manual on Uniform Traffic Control Devices

Source: Getty Images.

EMERGENCY VEHICLE PREEMPTION MAY 

ADDRESS THE FOLLOWING RISK FACTORS: 

Intersection Crossing Conflicts and Clearance Times.

25

TIER 3: MANAGE CONFLICTS IN TIME
TIER 4: 

INCREASE ATTENTIVENESS 

AND AWARENESS

Increasing attentiveness and awareness involves alerting roadway users to certain types of conflicts so that appropriate action 

can be taken consistent with the SSA principle that responsibility is shared. 

ENHANCED PAVEMENT 

MARKINGS 

WHAT IS IT?

Enhanced pavement markings include wider edge 

lines, retroreflective pavement markings, in-lane 

pavement markings, in-lane curve warning markings, 

and more. 

HOW DOES IT ALIGN WITH THE SSA?

Enhanced pavement markings aim to increase driver 

awareness and attentiveness of the travel lane, 

surrounding roadway, or upcoming roadway context 

changes. Increasing awareness of the roadway 

supports the Safe Roads Element of the Safe System 

Approach and the principle that redundancy is 

crucial. 

WHAT ARE THE BENEFITS OF 

ENHANCED PAVEMENT MARKINGS?

Wider edge lines may reduce non-intersection-related fatal and serious 

injury crashes on rural two-lane roads by up to 37 percent and fatal and 

serious injury crashes on rural freeways by up to 22 percent.38

Providing “Stop Ahead” pavement markings at stop-controlled intersections 

at forty-one sites in four States resulted in a 66 percent reduction in all traffic 

crash types and severity when applied on rural two-lane roadways with a 

minimum of 105 AADT to a maximum of 4,800 AADT on major roadways, and 

a minimum of 25 AADT to a maximum of 1,770 AADT on minor roadways.39 

 In-lane curve warning pavement markings may reduce all crashes by 35 to 38 percent.40

THIS COUNTERMEASURE IN PRACTICE

The adoption of wider edge lines was evaluated on rural, two-lane roadways in Kansas, Michigan, and Illinois. The 

study indicated a 15 to 30 percent reduction in total crashes.41

ENHANCED PAVEMENT MARKINGS 

MAY ADDRESS THE FOLLOWING 

RISK FACTORS: 

High/Excessive Vehicle Speeds, 

No Lighting, Undivided Roadway, 

and Curvature.

Source: Getty Images.

26
INTERSECTION CONFLICT WARNING SYSTEMS 

WHAT IS IT?

Intersection conflict warning systems (ICWS) use a vehicle sensor to detect the presence of vehicles approaching the 

intersecting roadway. The sensor triggers a warning message (such as “Vehicle Entering When Flashing” or “Crossing Traffic 

When Flashing”) and flashing light beacons to warn drivers of the potentially conflicting vehicle approaching the intersection. 

ICWS are often implemented in rural areas at non-signalized, stop-controlled intersections.

HOW DOES IT ALIGN WITH THE SSA?

ICWS provide drivers with a warning in real-time of potential crossing conflicts. These systems are intended to reduce crash 

frequency by increasing driver attentiveness and awareness of potential roadway conflicts. 

WHAT ARE THE BENEFITS OF 

INTERSECTION CONFLICT WARNING SYSTEMS?

Installing an ICWS with a combination of overhead and advanced postmounted signs and flashers at four sites in three States resulted in a 30 

percent reduction in all traffic crash types and severity applied at rural 

two-lane, stop-controlled intersections.42

THIS COUNTERMEASURE IN PRACTICE

Since 2020, the Indiana Department of Transportation has implemented ICWS at non-signalized, stop-controlled 

highway intersections statewide to reduce the likelihood of severe traffic crashes. Drivers traveling on the major road 

will see a static ENTERING TRAFFIC WHEN FLASHING sign and flashing warning lights when a vehicle is waiting 

on the intersecting minor road. Drivers traveling on the minor road, in addition to the stop sign, will see a constantly 

illuminated TRAFFIC APPROACHING WHEN FLASHING sign and flashing warning lights when a vehicle is approaching 

the intersection on the major road.43

Source: ICWS Highway Roadway Diagram and Signage, 

Indiana Department of Transportation: https://www.in.gov/

indot/traffic-engineering/intersection-conflict-warning-systems/

.

INTERSECTION CONFLICT WARNING 

SYSTEMS MAY ADDRESS THE 

FOLLOWING RISK FACTORS: 

Obstructed Sight Distance and 

High/Excessive Vehicle Speeds.

27

TIER 4: INCREASE ATTENTIVENESS AND AWARENESS
WRONG WAY DRIVING COUNTERMEASURES 

WHAT IS IT?

Wrong way driving crashes occur when a vehicle travels in a direction opposing the legal flow of traffic and collides with a 

vehicle traveling in the proper direction. Several countermeasures may deter or prevent wrong way driving behavior, such as 

static signage and pavement markings (e.g., “Wrong Way” signs), dynamic alert systems (e.g., illuminated “Wrong Way’ signs 

providing flashing warnings when a vehicle traveling the wrong way is detected), or in-vehicle alert systems connected via 

vehicle-to-infrastructure (V2I) or vehicle-to-vehicle (V2V) technologies. 

HOW DOES IT ALIGN WITH THE SAFE SYSTEM APPROACH?

Countermeasures may increase driver awareness and attentiveness by providing visual warnings to deter and prevent wrong 

way driving, which reduces potential crash conflicts with vehicles traveling in the right direction. 

WHAT ARE THE BENEFITS OF 

WRONG WAY DRIVING COUNTERMEASURES?

Wrong way driving crashes are one of the most severe crash types, 

typically occurring on high-speed divided highways or access ramps. 

Wrong way driving countermeasures aim to reduce both crash 

occurrence and severity, while limiting illegal driving behaviors. 

THIS COUNTERMEASURE IN PRACTICE

To combat wrong way driving, the Texas Department of Transportation implemented enhanced LED wrong way signs at 

28 exit ramps along Highway 281, resulting in a 35 percent reduction in the average monthly rate of logged wrong way 

driving events between 2012 to 2016. In addition, the Texas Department of Transportation implemented radar detection 

devices on overhead sign bridges along I-10 and I-35 to detect wrong way driving vehicles, which trigger a wrong way 

warning sign and flashing LED lights to catch the driver’s attention, while also providing a warning message to oncoming drivers that a vehicle is traveling in the wrong direction.44

WRONG WAY DRIVING 

COUNTERMEASURES MAY ADDRESS 

THE FOLLOWING RISK FACTORS: 

Obstructed Sight Distance, Ramp Geometry, 

and Driver Uncertainty and Confusion

Source: Wrong Way Driving Countermeasures, FHWA: 

https://highways.dot.gov/sites/fhwa.dot.gov/files/2022-07/WWD%20National%20Workshop%20Presentation.pdf.

28
Source: Getty Images.

BICYCLE TREATMENTS

WHAT IS IT?

Bicycle treatments include intersection bicycle boxes, bicycle signal 

heads and phases, and green colored pavement markings that aim to 

enhance the visibility of bicyclists on the roadway. The context of the 

roadway, including the composition and volumes of roadway users, 

vehicle speeds, and surrounding land uses will determine which bicycle 

treatments are most appropriate. 

HOW DOES IT ALIGN WITH THE SSA?

Bicycle treatments increase driver awareness and attentiveness of 

bicyclists, promote bicyclist visibility and priority in the roadway, reduce 

potential conflict points, and provide designated routes for bicycle 

movements. For example, green colored pavement markings remind 

motor vehicles that space on the roadway is shared with bicyclists, 

which may encourage drivers to reduce their travel speeds. Bicycle signal 

heads can also be considered a Tier 3 countermeasure to separate 

conflicts in time if a separate bicycle phase is provided or if the bike 

signals provide for a longer intersection clearance interval for cyclists

WHAT ARE THE BENEFITS OF 

BICYCLE TREATMENTS?

By making drivers more aware of bicycle movements, they are more 

likely to avoid crashes. For example, colored bicycle treatments were installed at signalized intersections in New Zealand and 

Australia at locations where bicyclists previously shared the roadway with motor vehicles, resulting in a 39 percent reduction in 

vehicle/bicycle crash types.45

THIS COUNTERMEASURE IN PRACTICE

According to an evaluation of 12 bike boxes implemented at signalized intersections in Portland, Oregon, the bike 

boxes reduced bicycle-motor vehicle conflicts at all improved intersections. Additionally, 77 percent of bicyclists felt 

that traveling through the intersection was safer after instillation of a bicycle treatment.46

BICYCLE TREATMENTS MAY ADDRESS 

THE FOLLOWING RISK FACTORS: 

Lack of Pedestrian/Cyclists Space 

Separation, Obstructed Sight Distance, and 

Intersection Crossing Conflict.

Source: Green Colored Paint, FHWA:

Improving Intersections for Pedestrians and Bicyclists: 

Informational Guide (dot.gov).

29

TIER 4: INCREASE ATTENTIVENESS AND AWARENESS
TRANSVERSE RUMBLE STRIPS

WHAT IS IT?

Transverse rumble strips are placed perpendicularly across the travel lane to warn drivers when approaching upcoming 

roadway changes that may not be anticipated by the driver. Transverse rumble strips are low-cost roadway improvements that 

may be used in both urban and rural areas to warn drivers of changing conditions, such as approaching minor stop-controlled 

intersections, horizontal curves, or work zones. 

HOW DOES IT ALIGN WITH THE SAFE SYSTEM APPROACH?

Transverse rumble strips provide a tactile and audible warning for drivers to alert them of upcoming traffic approaches while 

encouraging speed reduction through roadway design. 

WHAT ARE THE BENEFITS OF 

TRANSVERSE RUMBLE STRIPS?

Transverse rumble strips are a low-cost strategy with proven applications for 

stop-controlled intersections, approaches to horizontal curves, or in advance 

of work zones. In addition, transverse rumble strips resulted in a 36 percent 

reduction in fatal and serious injury crashes when applied as a traffic calming 

device on local roadways in both urban and suburban areas.47

THIS COUNTERMEASURE IN PRACTICE

Transverse rumble strips were evaluated on rural roadways in Iowa and Minnesota to examine their impacts on both 

total crashes and specific crash types such as right angle and run stop sign crashes. The analysis indicated a 23 

percent reduction in fatal and serious injury crashes.48

Source: Getty Images.

TRANSVERSE RUMBLE STRIPS MAY 

ADDRESS THE FOLLOWING RISK 

FACTORS: 

Horizontal Curvature and High/

Excessive Vehicle Speeds.

30
DYNAMIC SPEED FEEDBACK SIGNS 

WHAT IS IT?

Dynamic speed feedback signs (DSFS) are traffic control devices that provide a message 

to drivers when they exceed a certain speed threshold. A DSFS system typically uses 

a speed measuring device and a message sign to display feedback to drivers. DSFSs 

may be used in various applications such as school zones, work zones, and community 

entrances. 

HOW DOES IT ALIGN WITH THE SSA?

A DSFS alerts drivers when they are speeding and creates a sense of being monitored, 

reminding drivers of their shared responsibility to drive safely. A DSFS acts as a traffic 

calming device and encourages drivers to reduce speeds. 

WHAT ARE THE BENEFITS OF 

DYNAMIC SPEED FEEDBACK SIGNS?

Applying dynamic speed 

feedback signs on rural 

two-lane curves may result in 

traffic crash reductions from 

5 to 7 percent.49

THIS COUNTERMEASURE IN PRACTICE

The City of Bellevue (WA) evaluated two DSFS systems on urban two-lane roads with 25 to 35 mph speed limits. The first 

system implemented a “your speed” sign and the second system displayed the vehicle speed for vehicles traveling over 

the posted speed limit. An average speed reduction of 4.2 mph was documented after the first year of implementation, 

while an average speed reduction of 6.2 mph was documented four to eight years after installment.50

RESOURCES

Additional information to support Tier 4 – Increase Attentiveness and Awareness:

Guidance for the Design and Application of Shoulder and Centerline Rumble Strips

MUTCD Interim Approval 21 – RRFBs at Crosswalks

Manual for Uniform Traffic Control Devices

BIKESAFE Intersection Markings

NACTO Transit Street Design Guide

Self-Enforcing Roadways: A Guidance Report

Source: Cambridge Systematics, Inc. 

DYNAMIC FEEDBACK SIGNS MAY ADDRESS 

THE FOLLOWING RISK FACTORS: 

Travel Speeds.

31

TIER 4: INCREASE ATTENTIVENESS AND AWARENESS
Endnotes

1 OSHA, Practices for Safety and Health Programs: Identifying Hazard Control Options: The Hierarchy of Controls (osha.gov)

2 D. McTiernan and A. Rensen. “The Safe System Hierarchy of Control Framework for Local Roads,“ in Australasian Road Safety

Conference (Canberra, ACT, Australia: September 2016).

3 Ederer et al. The Safe Systems Pyramid: A new framework for traffic safety, Transportation Research Interdisciplinary Perspectives, 

Volume 21, 2023: https://www.sciencedirect.com/science/article/pii/S2590198223001525

4 Minnesota Department of Transportation, Complete Streets Case Studies: 

https://www.dot.state.mn.us/complete-streets/examples.html

5 Insurance Institute for Highway Safety (IIHS), Roundabouts: https://www.iihs.org/topics/roundabouts

6 Conversion of Signalized Intersection Into Single or Multi-lane Roundabout (CMF ID:4195), Crash Modification Factors 

Clearinghouse: https://www.cmfclearinghouse.org/detail.php?facid=4195

7 Insurance Institute for Highway Safety (IIHS), Roundabouts: https://www.iihs.org/topics/roundabouts

8 Replacement of Traditional Intersection with Roundabout with a Grade Separated Cycle Path (CMF ID: 2944), Crash Modification 

Factors Clearinghouse: https://www.cmfclearinghouse.org/detail.php?facid=2944

9 FHWA, Diverging Diamon Interchange: An Innovative, Proven Solution for Improving Safety and Mobility At Interchanges: 

https://safety.fhwa.dot.gov/intersection/crossover/fhwasa14039.pdf

10 Convert Diamond Interchange to Diverging Diamond Interchange (CMF ID: 10762), Crash Modification Factors Clearinghouse: 

https://www.cmfclearinghouse.org/detail.php?facid=10762

11 Convert At-Grade Intersections to Diverging Diamond Interchanges (CMF ID: 9658), Crash Modification Factors Clearinghouse: 

https://www.cmfclearinghouse.org/detail.php?facid=9658

12 Convert Traditional Bike Lanes to SBL With Flexi-Posts (CMF ID: 11294), Crash Modification Factors Clearinghouse: 

https://www.cmfclearinghouse.org/detail.php?facid=11294

13 The City of Philadelphia, Philadelphia PSBL Study: 

https://www.phila.gov/media/20220401143557/Philadelphia-PSBL-Study__Task-5_Final-Report_6.30.21-3.pdf

14 FHWA, Medians and Pedestrian Refuge Islands in Urban and Suburban Areas: https://highways.dot.gov/safety/proven-safetycountermeasures/medians-and-pedestrian-refuge-islands-urban-and-suburban-areas

15 NACTO, Create Safety In Numbers: https://nacto.org/wp-content/uploads/2017/11/dot-making-safer-streets.pdf

16 Install Wire Guardrails Between Lanes of Opposing Traffic (CMF ID: 53), Crash Modification Factors Clearinghouse: 

https://www.cmfclearinghouse.org/detail.php?facid=53

17 Katherine Burns, Performance Evaluation of a Cable Median Barrier System on an Oregon Highway with a Narrow Median: 

https://journals.sagepub.com/doi/epdf/10.3141/2588-15

18 Kentucky Transportation Cabinet, Design Guidance for Shared Four-Lane (2+1) Roadways: 

https://transportation.ky.gov/Highway-Design/Memos/04-13.pdf

19 Texas Department of Transportation, Super 2 Research: Two Decades of Super 2 Research and Implementation for TxDOT 

Continues to Produce Benefits — Texas A&M Transportation Institute (tamu.edu): https://tti.tamu.edu/researcher/two-decades-ofsuper-2-research-and-implementation-for-txdot-continues-to-produce-benefits/

20 FHWA, Rural Roadway Departure Countermeasure Pocket Guide: 

https://safety.fhwa.dot.gov/FoRRRwD/RwDPocketGuide.pdf

21 Minnesota Department of Transportation, Reducing Fatal Crashes on U.S 14: 

https://www.mnltap.umn.edu/publications/exchange/2015/spring/us14.html

22 S.G Charlton (University of Waikato & TERNZ Ltd) and P.H Bass (LERNZ Ltd), Speed Change Management for New Zealand Roads:

https://nzta.govt.nz/assets/resources/research/reports/300/docs/300.pdf

23 FHWA, Case Study 2: Noteworthy Speed Management Practices, Self-Enforcing Roadways (City of Golden, CO): 

https://highways.dot.gov/safety/speed-management/noteworthy-practice-booklet-speed-management/case-study-2-noteworthy-speed

24 PEDSAFE, Raised Pedestrian Crossings: http://pedbikesafe.org/pedsafe/countermeasures_detail.cfm?CM_NUM=7

25 Install Raised Pedestrian Crosswalks (CMF ID: 136), Crash Modification Factors Clearinghouse: 

https://www.cmfclearinghouse.org/detail.php?facid=136 

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26 PEDSAFE, Granite Street Traffic Calming: http://pedbikesafe.org/pedsafe/casestudies_detail.cfm?CM_NUM=7&CS_NUM=20

27 Construct Gateway Monument (CMF ID: 2430), Crash Modification Factors Clearinghouse: 

https://www.cmfclearinghouse.org/detail.php?facid=2430

28 Michigan Department of Transportation, User guide for R1-6 Gateway Treatment for Pedestrian Crossings: 

https://aii.transportation.org/documents/User%20Guide_2018_0503_Final_UPDATED%20CDM%20Edgeline%20Clarification.pdf

29 Install Speed Humps (CMF ID: 134), Crash Modification Factors Clearinghouse: 

https://www.cmfclearinghouse.org/detail.php?facid=134

30 FHWA, Module 8: Traffic Calming Case Studies – New York City Neighborhood Slow Zone Program: 

https://highways.dot.gov/safety/speed-management/traffic-calming-eprimer/module-8-traffic-calming-case-studies

31 Change Permissive Left-Turn Phasing to Protected/Permissive (CMF ID: 5597), Crash Modification Factors Clearinghouse: 

https://www.cmfclearinghouse.org/detail.php?facid=5597

32 FHWA, Intersection Safety Case Study – Permissive/Protected Left-Turn Phasing: 

https://rosap.ntl.bts.gov/view/dot/41466/dot_41466_DS1.pdf

33 International Conference on Road Safety and Simulation, Optimizing Signal Timings to Improve Safety of Signalized Arterials: 

https://onlinepubs.trb.org/onlinepubs/conferences/2011/RSS/2/Stevanovic,Al.pdf

34 New York City Department of Transportation, Arterial Slow Zones: 

https://www.nyc.gov/html/visionzero/pages/initiatives/street-design.shtml

35 Implement Barnes Dance (CMF ID: 4117), Crash Modification Factors Clearinghouse: 

https://www.cmfclearinghouse.org/detail.php?facid=4117

36 University of California Traffic Safety Center, Oakland Chinatown Pedestrian Scramble: 

https://escholarship.org/content/qt3fh5q4dk/qt3fh5q4dk_noSplash_0c40a86ce1824714aa8de64ac81daacf.pdf?t=krnbre

37 NHTSA, Traffic Signal Preemption for Emergency Vehicles: 

https://www.gtt.com/wp-content/uploads/Traffic-signal-preemption-for-emergency-vehicles-A-cross-cutting-study.pdf

38 FHWA, Proven Safety Countermeasures – Wider Edge Lines: 

https://highways.dot.gov/sites/fhwa.dot.gov/files/2022-08/PSC_New_Wider%20Edge%20Lines_508.pdf

39 Provide “Stop Ahead” Pavement Markings (CMF ID:9072), Crash Modification Factors Clearinghouse: 

https://www.cmfclearinghouse.org/detail.php?facid=9072

40 FHWA, Enhanced Delineation for Horizontal Curves: 

https://highways.dot.gov/safety/proven-safety-countermeasures/enhanced-delineation-horizontal-curves

41 Eun Sug Park (Texas Transportation Institute), Paul J. Carlson (Texas A&M University), Richard J. Porter (University of Utah), Carl K. 

Anderson (turner-Fairbank Highway Research Center), Safety Effects of Wider Edge Lines on Rural, Two-Lane Highways: 

https://www.sciencedirect.com/science/article/abs/pii/S0001457512000486?via%3Dihub

42 Install an Intersection Conflict Warning System with a Combined of Overhead and Advanced Post Mounted Signs and Flashers (CMF 

ID: 8474), Crash Modification Factors Clearinghouse: 

https://www.cmfclearinghouse.org/detail.php?facid=8474

43 Indiana Department of Transportation, Intersection Conflict Warning Systems: 

https://www.in.gov/indot/traffic-engineering/intersection-conflict-warning-systems/

44 Texas Department of Transportation, Enterprise Countermeasures for Wrong-Way Driving on Freeways: 

https://enterprise.prog.org/Projects/2013/wrongway/ENT_Countermeasures_WrongWayDriving_FINAL_Sept2016.pdf

45 Installation of Colored Bicycle Lanes at Signalized Intersections (CMF ID: 3258), Crash Modification Factors Clearinghouse: 

https://www.cmfclearinghouse.org/detail.php?facid=3258

46 Portland State University, Evaluation of Bike Boxes at Signalized Intersections: 

https://pdxscholar.library.pdx.edu/cgi/viewcontent.cgi?article=1017&context=usp_fac

47 Install Transverse Rumble Strips as Traffic Calming Device (CMF ID: 139), Crash Modification Factors Clearinghouse: 

https://www.cmfclearinghouse.org/detail.php?facid=139

48 FHWA, Safety Evaluation of Transverse Rumble Strips on Approaches at Stop-Controlled Intersections in Rural Areas: 

https://www.fhwa.dot.gov/publications/research/safety/hsis/12047/index.cfm

49 Iowa State University, Dynamic Speed Feedback Signs: 

https://intrans.iastate.edu/app/uploads/2018/03/DSFS_tech_brief1.pdf

50 Iowa State University, Dynamic Speed Feedback Signs: 

https://intrans.iastate.edu/app/uploads/2018/03/DSFS_tech_brief1.pdf

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FHWA-SA-22-069