What is the maximum allowable width of roadways to avoid exposure to roof fall danger?

The correct answer is based on safety regulations and best practices in mining operations, especially regarding the stability of mine roofs. The maximum allowable width of roadways being set at 20 feet, unless additional support is added, is determined by the need to maintain a safe working environment while ensuring that the structural integrity of the mine is not compromised.

When roadways exceed this width without adequate support, the risk of roof falls increases significantly. The rule acknowledges that while 20 feet is a standard limit, certain conditions—such as geological features or the materials used in construction—may require additional support mechanisms to safely expand beyond that width. This flexibility allows for adaptations based on specific site conditions, ensuring that miners work in a safer environment.

In contrast, the other options suggest either broader widths without additional support or rigid limits that do not account for varying conditions. Such measures would not adequately protect miners from the dangers associated with roof stability, particularly in areas known to have potential fall risks. Hence, the policy encourages safe practices while recognizing that more support may be necessary in challenging conditions.