Safety Investigation and Design Guidance for Curbs Near Energy-Absorbing End Terminals
Jennifer Schmidt, Bob Bielenberg, Brock Schroder, Ronald Faller, Karla Lechtenberg
Guardrail end terminals have been developed to shield the end of a longitudinal barrier and function as a redirective barrier when struck along the side. The use of curbs is often desired adjacent to guardrail and end terminals due to restricted right-of-way, drainage considerations, access control, and other functions. Curbs can adjacent to guardrail have resulted in some unsuccessful crash tests. However, the safety performance of energy-absorbing end terminals installed adjacent to curbs and gutters is unknown. Little guidance is available to State Departments of Transportation that desire installations with curbs adjacent to energy-absorbing guardrail end terminals. The objective of this research study was to investigate whether curb placement in advance of guardrail end terminals significantly degrades system performance. A generic, energy-absorbing, W-beam end terminal model was developed using LS-DYNA computer simulation software to represent existing, energy-absorbing, compression-based, end terminal systems. These systems include an impact head with a guide chute placed over the rail end, which dissipates an errant vehicle’s kinetic energy when propelled downstream through changes to the rail shape. Impacts on the end of the terminal were evaluated according to NCHRP Report 350 and Manual for Assessing Safety Hardware (MASH) 2009 safety performance criteria. The simulations were compared to results from available crash tests to ensure that the energy-absorbing, end terminal model accurately represented the performance of end terminals. Curbs that were 2 to 6 in. high with a sloped or vertical shape were laterally offset 0 in., 6 in., and 6 ft away from the face of the Midwest Guardrail System model. Additionally, flared tangent end terminal performance was also evaluated. The safety performance of the system with and without curbs was compared, and general performance trends were identified.
Highway Safety, LS-DYNA FEA, Computer Simulation, NCHRP Report 350, MASH, TL-3, Energy-Absorbing End Terminals, Guardrail End Terminals, Curbs