| Abstract: | U-turn lanes are commonly provided at diamond interchanges to reduce delays for U-turning traffic and for the interchange as a whole; however, there are currently many unknowns related to their design, operation, and use. This project provides the Texas Department of Transportation (TxDOT) with implementable guidelines for designing and operating U-turn lanes at diamond interchanges. Researchers identified and investigated several factors affecting U-turn lane use, determined the performance and limitations of U-turn lanes under various geometric and operational conditions, and determined the anticipated effectiveness of proposed solutions to U-turn operational issues. Researchers then developed and structured guidelines for inclusion in the TxDOT Roadway Design Manual and other manuals addressing access management, design, and operations of U-turn facilities. This investigative effort included a cross-sectional safety analysis of existing U-turn configurations that provided valuable insight into factors contributing to U-turn safety. Along with the safety analysis, researchers developed a self-calculating spreadsheet tool that can be used to predict U-turn safety performance under various conditions. |
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