AACN

advanced automatic crash notification

ACN

automatic crash notification

ALR/ALS

administrative license revocation or suspension

BAC

blood alcohol concentration

crash diagnoses

CMF

crash modification factor

DOT

department of transportation

DUI

driving under the influence

EMS

emergency medical services

EMT

emergency medical technician

IRA

injury risk assessment

ISA

intelligent speed assist

ITS

intelligent transportation systems

km/h

kilometers per hour

LOS

level of service

mph

miles per hour

NCAP

New Car Assessment Program

NG911

Next Generation 911

NSC

National Safety Council

PCC

professional and community coordination

PERF

Police Executive Research Forum

standard deviation

STEER

Strengthening Traffic Enforcement, Education, and Responsibility

VMT

vehicle miles traveled

VSL

variable speed limits

WHO

World Health Organization

A Guide to Applying the Safe System Approach to Transportation Planning, Design, and Operations
2025

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The Safe System approach is a holistic approach that provides a framework for making the U.S. national transportation system safer. It is based on building and reinforcing multiple layers of protection to prevent crashes from happening and minimize the harm caused when crashes occur. This safety approach differs from conventional ones because it focuses on human vulnerability and creates a system with many redundancies to protect all transportation users.

NCHRP Research Report 1135: A Guide to Applying the Safe System Approach to Transportation Planning, Design, and Operations, from TRB's National Cooperative Highway Research Program, presents information for applying the Safe System approach among state departments of transportation and other transportation agencies.

Supplemental to the report is NCHRP Web-Only Document 413: Applying the Safe System Approach to Transportation Planning, Design, and Operations.

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Implementation Plan
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Publication information

102 pages · 8.5 x 11 · paperback
ISBN Paperback: 0-309-99350-4
ISBN Ebook: 0-309-99352-0
DOI: https://doi.org/10.17226/29147

Suggested citation

National Academies of Sciences, Engineering, and Medicine. 2025. A Guide to Applying the Safe System Approach to Transportation Planning, Design, and Operations. Washington, DC: The National Academies Press.

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Front Matter i-x
Summary 1-2
1 Background of the Safe System 3-9
2 Safe System Policy 10-19
3 Safe System Planning 20-27
4 Safe System Design 28-37
5 Safe System Operations and Maintenance 38-48
6 Safe System Law Enforcement 49-56
7 Safe System Post-Crash Response 57-64
Acronyms and Abbreviations 65-65
References 66-72
Appendix A: Safe System Policy Practices 73-74
Appendix B: Safe System Planning Practices 75-76
Appendix C: Safe System Design Practices 77-78
Appendix D: Safe System Operations and Maintenance Practices 79-80
Appendix E: Safe System Law Enforcement Practices 81-82
Appendix F: Safe System Post-Crash Response Practices 83-84
Appendix G: Safe System Strategy Implementation Self-Assessment 85-92

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A Guide to Applying the Safe System Approach to Transportation Planning, Design, and Operations (2025)

Chapter: Acronyms and Abbreviations

Acronyms and Abbreviations