What is referred to by a barrier along the open sides of stairways and platforms that prevents falling?

A guardrail is a critical safety feature designed to prevent falls from elevated surfaces such as stairways and platforms. The primary purpose of a guardrail is to act as a physical barrier that can stop or redirect individuals from falling over the edge. Guardrails are typically constructed to meet specific safety standards, ensuring they are sturdy enough to withstand impact and effectively provide protection.

In contrast, a handrail, while also a safety feature, is primarily used to assist individuals in maintaining balance while ascending or descending stairs, rather than preventing falls from the open sides. Safety nets are used in construction and various work environments to catch individuals who may fall from heights, but they do not serve as physical barriers on the edges of stairways or platforms. A fall arrest system includes equipment designed to stop a fall in progress, helping to reduce the risk of injury, but it doesn't function as a physical barrier like a guardrail does. Thus, the guardrail is the most appropriate term for a barrier along open sides that prevents falling.