Turner-Fairbank Highway Research Center

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FHWA Technical Report - Safety Analysis of Interchanges

Product Type

Research Report


Torbic, D.J., D.W. Harwood, D.K. Gilmore, and K.R. Richard




The objectives of this research are to synthesize the current state of knowledge concerning the safety assessment of new or modified interchanges; develop a spreadsheet-based computational tool for performing safety assessments of interchanges; and identify gaps in knowledge concerning interchange safety assessment and future research needs to fill those gaps. This report summarizes the capabilities of the spreadsheet-based Interchanges Safety Analysis Tool (ISAT), summarizes safety data related to interchanges, summarizes safety literature related to interchanges, presents results of telephone interviews with key stakeholders to investigate their needs and requirements in safety evaluations of interchanges, and identifies substantive gaps in the current state of knowledge that limit the ability of ISAT to provide all of the capabilities desired by potential users and provides a brief summary of the needed research to address these gaps. This report also contains the detailed algorithms utilized in the calculations of the ISAT program. the other primary deliverables of this research are (1) the spreadsheet-based analytical tool (i.e., ISAT) and (2) an accompanying user manual (FHWA-HRT-07-045) which provides detailed descriptions/instructions on the usage and operation of ISAT.

Link To Research Report

FHWA Technical Report - Safety Analysis of Interchanges


geometric design
safety performance function

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HSIS Summaries

HSIS Summary Reports are two to eight pages in length and include a brief description of the issue addressed, data used, methodology applied, significant results, and practical implications.

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Research Reports

A variety of research studies have been performed using data from HSIS. Many of the final reports prepared are now available electronically.

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Technical Summaries

Research reports are often summarized in executive summaries, technical briefs, or other abbreviated formats. Included here are those road safety summaries that involved research using HSIS data.

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Safety Analysis Tools

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