Synthesis of System/Vehicle Interaction Similarities/Dissimilarties with 12-inch versus 8-inch Blockouts with 31-inch Mounting Height, Mid-Span Splices (601621)

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Final Report Link:  Synthesis of System/Vehicle Interaction Similarities/Dissimilarities with 12-inch VS 8-inch Blockouts with 31-inch Mounting Height, Mid-Span Splices


TTI Research Supervisor:
Chiara Silvestri Dobrovolny, Ph.D
Associate Research Scientist
Texas A&M Transportation Institute
3135 TAMU
College Station, Texas 77843-3135
(979) 845-8971
[email protected]
Pooled Fund Technical Representative:
Al Hangul, P.E.
Civil Engineering Manager I, Design Division
Tennessee Department of Transportation
Suite 1300
James K. Polk State Office Building
Nashville, TN 37243-0348
(615) 741-0840
[email protected]


Full scale crash tests have been performed with use of a 31-inch guardrail with 12-inch blockouts and mid-span splices under a variety of impact conditions. Thus, the behavior of this test article has been fairly well documented. Certain DOTs prefer continued use of standard 8-inch blockouts to reduce inventory and simplify guardrail repair. A desire was raised from some States to receive eligibility for use on the NHS for configurations of 31-inch guardrail with 8-inch blockouts for configurations initially tested with 12-inch blockouts.

The purpose of this research was to review and compare system performance and vehicle interaction in full-scale crash tests of 31-inch guardrail with 12-inch and 8-inch blockouts. The information compiled from this research will enable the Federal Highway Administration and State Departments of Transportation to decide whether use of 8-inch deep blockouts can be considered a crashworthy alternative for configurations initially tested with a 31-inch guardrail with 12-inch blockouts.

To identify similarities and dissimilarities from use of 12-inch and 8-inch blockout depth, data collected through the crash events was then compared with respect to vehicle angular displacements (i.e., yaw, pitch, and roll angles), occupant risks (impact velocities and ridedown accelerations), rail system deflections (dynamic and permanent), and working width, and vehicle interaction with guardrail system through the impact event. Chapter 4 reports findings related to the comparison of vehicle angular displacements, and Chapter 5 compares longitudinal and lateral occupant impact velocities and ridedown accelerations. Information regarding rail system dynamic, permanent deflections, and working width is collected in Chapter 6. Chapter 7 includes an analytical study of after-impact lateral rail trajectory with respect to blockout depth use, and presents an evaluation of vehicle interaction with the rail system during the impact event. Summary and research conclusions are reported in Chapter 8.