The National Academies

NCHRP 17-116 [Active]

Practical Approaches to Quantifying Safe System Concepts

  Project Data
Funds: $450,000
Staff Responsibility: David M. Jared
Research Agency: Vanasse Hangen Brustlin
Principal Investigator: Michael Dunn
Effective Date: 4/5/2024
Completion Date: 4/4/2027


To reverse the upward trend in traffic fatalities, many state departments of transportation (DOTs) are interested in moving toward a Safe System (SS) approach and are considering practical ways to mitigate conflicts and reduce the force of crashes on roadways and at intersections. In some cases, this has resulted in the development of policy changes in design and speed management. 

The SS approach applies to all types of roadways, both urban and rural. However, practitioners require methods and tools for quantifying, analyzing, and evaluating the safety benefits of different design and operational alternatives. For example, the FHWA report, A_Safe_System_Based_Framework_and_Analytical_Methodology_for_Assessing_Intersections (FHWA-SA-21-008), provides a method for developing a Safe System Index (SSI) score and other SS-related metrics that quantify exposure, complexity, and severity associated with different crash types at intersections. This method also provides a basis for the assessment of a wide selection of intersections, including signalized urban intersections and rural uncontrolled intersections. 

While the SSI method can be applied at a project level and be incorporated into an Intersection Control Evaluation alternative screening process to provide another metric for safety, it requires several high-level assumptions to be included in the analysis. State DOTs may be reluctant to adopt these assumptions and utilize this method without some level of validation. Research is needed to review existing frameworks and methods, develop new methods or modify existing methods, validate the methods, and provide resources to state DOTs and local agencies for implementation.


The objective of this research is to develop or modify methods for quantifying the benefits of applying SS principles to various intersection designs.  



Task 1. Conduct preparations for stakeholder outreach. 

Task 1a. Conduct a focused literature review. The review should not be a history of SS but focus on innovations with methods that quantify the benefits of SS principle applications to various intersection designs for all travel modes and road users. 

Task 1b. Develop a stakeholder outreach plan. Determine which state DOTs and local agencies are applying or planning to apply SS principles to intersection designs and any data that can be applied to this research. The plan shall be submitted to NCHRP for approval. NCHRP approval is required before work on subsequent tasks begins. 

Task 2. Conduct stakeholder outreach. Identify stakeholders interested in participating in a virtual workshop.    

Task 3. Prepare a research plan for method development or modification. Based on the findings from Tasks 1 and 2, prepare a research plan to develop methods or propose modifications to existing methods. The methods must be practical and based on inputs readily available to practitioners during the scoping and preliminary phases of project development. Identify and acquire data sources to be used in validating the methods. 

Task 4. Submit an interim report. The report shall include (1) the findings from Tasks 1 and 2, including potential participation from stakeholders in Phase II tasks, and (2) the research and validation plans from Task 3. Findings from the report shall be presented to NCHRP at an in-person meeting. Travel expenses for panel members are covered by NCHRP. Approval of the report is required by NCHRP before work on subsequent tasks may begin.  


Task 5. Develop and validate new or modified methods. Submit a technical memorandum on development and validation results and proposed revisions to new or modified methods for NCHRP approval. NCHRP approval of the technical memorandum is required before work on the subsequent tasks may begin. 

Task 6. Conduct a virtual stakeholder workshop. Obtain feedback from stakeholders on the validated methods and implementation of these methods via an interactive workshop. Based on feedback received in the workshop, make final adjustments to the methods and develop an implementation plan for state DOTs and local agencies for applying the methods to intersection projects. 

Task 7. Submit final deliverablesDeliverables shall include (1) a conduct of research report summarizing the research effort; (2) the new methods or modifications; (3) the implementation plan for state DOTs and local agencies (see Special Note I); and (4) a slide summary of the research. 

Note: Following receipt of the preliminary draft final deliverables, the remaining 3 months shall be for NCHRP review and comment and for research agency preparation of the revised final deliverables.


STATUS: Research is in progress. 

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