In traffic engineering, highway guardrail may prevent an errant vehicle from impacting roadside obstacles which may be either man-made (sign structures, culvert inlets, utility poles) or natural (trees, rock croppings), running off the road and going down a steep embankment, or veering off the roadway into oncoming traffic (commonly referred to as a median barrier). A secondary objective is keeping the vehicle upright while deflected along the guardrail. The most common type of guardrail in use today is the Thrie-beam. Thrie-beam guardrail consists of wood posts and wood spacer blocks or steel posts with wood spacer blocks. The wood spacer blocks reduce or minimize a vehicle snagging on the posts upon impact. In addition, a blockout may be used to increase the offset of guardrail with an obstacle such as a curb. The posts’ primary purpose is to maintain the height of the guardrail during the initial stages of post deflection. Maintaining guardrail height also reduces the potential for a vehicle to vault over the guardrail upon initial impact. The posts also play a role in the amount of resistance and deflection a guardrail may experience during impact. Resistance in a strong post system results from a combination of tensile and flexural stiffness of the rail and the bending and shearing resistance of the posts.