Crash analysis and evaluation of a new separate W-beam guardrail on highways using the finite element method

In terms of highway traffic safety, the W-beam guardrail plays an essential role in absorbing impact energy, reducing occupant acceleration peaks, and redirecting the vehicle in the correct direction. In this study, a new separate W-beam guardrail named “SWG” composed of separate posts connected by bolts was invented to improve the safety performance of the guardrail. The new W-beam guardrail was compared with the traditional W-beam guardrail (TWG) by the finite element simulation method. The exit box criteria, occupant impact velocity (OIV), and occupant ride down acceleration (ORA) are utilized to evaluate occupant safety and injury risk. The collision results reveal that the new W-beam guardrail performs better than the TWG and can effectively reduce the injury of the occupants and correct the driving direction of the out-of-control vehicle during the crash with a 1996 Dodge Neon and a 2007 Chevy Silverado, respectively. Additionally, it is found that the strength and installation of the bolts and the working width significantly affect the safety performance of the new W-beam guardrail. After conducting multiple sets of simulation tests, the optimal guardrail design meeting the requirements of the Neon and the Silverado is obtained. In this design, the values of OIVmax and ORAmax are 6.27 m/s and 50.3 m/s2 for Neon, and 4.57 m/s and 66.3 m/s2 for Silverado, respectively. Both vehicles can be guided out of the guardrail in the exit box criteria to avoid snagging.