Designated areas can only be used on top of:

Designated areas are specific locations within a work environment that are set up to safely allow certain activities or functions, particularly with respect to fall protection. In the case of low-slope roofs, these designated areas are vital because they are often associated with roofing work where the incline of the surface makes it challenging for workers to maintain balance and ensure safety.

Using designated areas on low-slope roofs provides a controlled and clearly marked space where workers can operate without the accompanying risks commonly found in other environments. Such spaces can incorporate fall protection measures and protocols that are essential for ensuring worker safety when performing tasks at height.

Other environments, such as equipment, trailers, and platforms, may not adequately address the specific fall hazards typically encountered on low-slope roofs; therefore, they do not serve the same purpose in terms of safety regulation under OSHA guidelines. Designated areas are primarily geared towards managing the risks associated with particular work types, especially when working on inclined surfaces like low-slope roofs, making them the most suitable choice in this context.