Evaluation of Guardrail to Concrete Bridge Rail Transitions

In December 2001, the Design Division and Bridge Division of Texas Department of Transportation released a new standard for an approach guardfence to concrete bridge rail transition that complies with the testing requirements of National Cooperative Highway Research Program (NCHRP) Report 350 for use on high-speed roadways. Because there are no national transition designs that have been developed and tested for lower speed conditions, the same transition standard is typically applied to all roadways regardless of speed. However, the new thrie beam transition design represents a significant increase in installation cost and complexity over the previous design. Thus, it may be cost prohibitive to require use of the same design on all roadways. The purpose of this research was to develop a transition that is suitable for use on lower speed roadways and that is less expensive and complex than the current high-speed design. A low-cost transition was successfully evaluated at 45 mph impact speeds under NCHRP Report 350 Test Level 2 conditions. A second objective of the project was to evaluate the need for the curb detail that is one of the design elements of the newly adopted thrie beam transition design. Elimination of the curb would greatly enhance installation flexibility and reduce installation cost. The assessment of the curb was accomplished through full-scale crash testing.