Which factor is least likely to affect stair safety?

When assessing stair safety, several physical characteristics contribute to the overall safety and usability of stairways. Among these, the uniformity of risers, width of treads, and guardrail height directly influence how safely individuals can navigate stairs. Each of these components is essential in establishing a predictable and secure environment for users.

The uniformity of risers is critical because inconsistent riser heights can lead to trips and falls, as users may anticipate a certain height and then misjudge their step. Similarly, the width of the treads greatly affects how people place their feet, directly impacting stability and balance. The height of guardrails is also vital as it serves as a protective barrier that can prevent falls from the stairs, particularly in open areas or where stairs are elevated.

In contrast, the color of the handrail, while it may play a role in visibility and aesthetic appeal, does not fundamentally impact the physical safety of the stair structure itself. Safety standards focus on dimensions and physical features that prevent accidents, while color is not a factor that contributes to the structure's integrity or usability in a significant way. Therefore, the color of the handrail is the least likely to affect stair safety.