Lanes for through movements that begin upstream of a signalized intersection and end downstream of the intersection—auxiliary through lanes (ATLs)—are recognized as a moderate-cost approach to increase intersection and overall corridor capacity. NCHRP Report 707 provides guidelines to use for justification, design, and analysis of ATLs at signalized intersections. The report is aimed to assist transportation professionals in the effective and safe use of intersection auxiliary through lanes. The research was performed by Kittelson & Associates, Inc., in association with the Institute for Transportation Research and Education (ITRE), Texas Transportation Institute (TTI), Write Rhetoric, and Quality Counts. Information was gathered via literature review and interviews with practitioners to inform the framework of the study. Data were collected from 22 ATL approaches across the United States. Statistical models were developed using field data to predict the amount of traffic expected to use the ATL. A safety study was conducted by examining 16 ATL approaches from eight intersections across the United States using a calibrated VISSIM model with FHWA’s Surrogate Safety Assessment Model (SSAM). The guidelines are accompanied by a final report posted on the TRB website as NCHRP Web-Only Document 178: Assessment of Auxiliary Through Lanes at Signalized Intersections along with a spreadsheet-based computational engine posted on the project web page (http://apps.trb.org/cmsfeed/TRBNetProjectDisplay.asp?ProjectID=2492).
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