Handrails on both sides of the stairs is a universal design feature that gives people options for stabilizing themselves when going up or down the stairs.
Extending the handrail one foot beyond the top and bottom step increases safety by helping people maintain balance. They also serve as a tactile alert for people with vision impairments (or anyone walking in the dark) to indicate a transition is about to occur. Additionally, if the stairwell changes direction, it’s good practice to curve the handrail around the walls for continued support.