Description: The TxDOT Design Division is in the process of developing new guardrail standards that comply with the AASHTO Manual for Assessing Safety Hardware (MASH). The new guardrail system will provide increased capacity and improved impact performance relative to the current design. A key feature of the new system is an increased in rail mounting height from 27 inches to 31 inches. TxDOT's current TL-2 metal beam transition is 27 inches tall and is not compatible with the new 31 inch guardrail system. While the high-speed, nested thrie beam transition system meets MASH guidelines and is compatible with a 31-inch guardrail, it would be cost-prohibitive to use it on all roadways. The objective of this research was to develop a transition that is suitable for use on lower speed roadways, less expensive and complex than the current high-speed (i.e., TL-3) transition design, and is compatible with a 31-inch guardrail. A low-cost guardrail-to-bridge rail transition was successfully developed and tested under MASH Test Level 2 conditions. It is compatible with a 31-inch guardrail and can connect to rigid concrete bridge rails. It is considered suitable for implementation on roadways that have traffic conditions appropriate for the use of TL-2 safety hardware. Use of this system provides significant savings in material and installation cost compared to the high speed transition system.
Date: December 2011
Creator: Bligh, Roger P.; Arrington, Dusty R. & Menges, Wanda L.
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