Abstract:
Several 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 in front of guardrail and end terminals, while undesirable, is often necessary due to restricted right-of-way, drainage considerations, access control, and other functions. Curbs can affect the interaction of errant vehicles with roadside barriers by affecting vehicle redirection and barrier loading. However the performance of energy-absorbing end terminals installed adjacent to curb and gutter is unknown. Little guidance is available to State Departments of Transportation (DOTs) who have installations where curbs are desired adjacent to energy absorbing, guardrail end terminals. The objective of this research study was to investigate whether curb placement in front of guardrail end terminals significantly degrades system performance. A generic energy-absorbing, W-beam end terminal model was developed to represent existing, compression-based, terminal systems LS-DYNA computer simulation software. All of these systems include an impact head with a guide chute that is placed over the rail end, which dissipates a vehicle’s kinetic energy when propelled downstream through changes to the rail shape. Impacts on the end of the terminal (test nos. 3-30, 3-31, 3-32, and 3-33) were evaluated according to NCHRP Report 350 and Manual for Assessing Safety Hardware (MASH) safety performance criteria. The simulations were compared to available crash tests data 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 offset 0 to 6 in. from the face of the Midwest Guardrail System (MGS) model. The performance of the system with and without curbs was compared, and general performance trends were identified.
