Publication Details


A safe system-based framework and analytical methodology for assessing intersections

Type: Paper

Subtype: Final report

Author(s): Porter, R. J.; Dunn, Michael; Soika, Jonathan; Huang, Ivy; Coley, Dylan; Gross, Annette; Kumfer, Wes; Heiny, Stephen

Publisher: Federal Highway Administration Office of Safety

Url: https://safety.fhwa.dot.gov/intersection/ssi/fhwasa21008.pdf

Publication Date: Jan-2021

Number: FHWA-SA-21-008

Address: Washington, DC

Abstract: This report presents a Safe System for Intersections (SSI) method that intersection planners and designers can readily implement, that dovetails with the typical U.S. project development process, and that uses commonly available projectlevel data. The SSI method is presented in the context of a Stage 1 Intersection Control Evaluation (ICE), at the scoping phase of project development where intersection alternatives are analyzed with respect to whether they meet project needs and are practical to pursue. The method incorporates concepts of conflict point identification and classification, exposure, kinetic energy transfer, conflict point severity, and intersection movement complexity. Application of the SSI method results in multiple measures of effectiveness (MOEs) and a set of SSI scores that characterize the extent to which anintersection alternative in a given context aligns with the principles of kinetic energy management and a Safe System. TheSSI MOEs and SSI scores can serve as additional safety metrics to inform the process of screening alternatives andidentifying an optimal solution for an intersection. The report includes an overview of Safe System concepts and principles, a detailed description of the SSI method, example project applications, and a future vision for the method.