A roadway guardrail system including a rail, a plurality of support posts, and a plurality of fasteners assembly to redirect an impacting vehicle and dissipate a portion of the impacting vehicle's energy. Block-outs may be positioned in between the rail and support posts. A plurality of support posts each includes a slot extending along its length aligning with apertures in the rail and engaging with the rail through the apertures with fasteners including reinforcing members slidable along the slots in the posts. Alternatively, the rail has a plurality of laterally extending slots aligning with apertures in support posts and engaging with the support posts through the apertures with fasteners including reinforcing members slidable along the slots.