When can the use of vibratory rollers be restricted or prohibited by the Engineer?

The correct response highlights a critical safety concern regarding the use of vibratory rollers. The Engineer may restrict or prohibit the use of these rollers when there's a risk of damaging underlying structures. Vibratory rollers utilize a mechanism that imparts vibration to improve the compaction of materials like asphalt or soil. However, this vibration can also transmit forces to nearby structures, which may lead to structural damage, particularly if those structures are sensitive or not adequately supported.

For example, if there are pipelines, buried electrical conduits, or even lightly built structures near the compaction zone, the vibrations can induce stresses that compromise their integrity. Thus, assessing the proximity of such structures is paramount, and the Engineer must prioritize safety by restricting the use of vibratory rollers in these situations to prevent any potential damage.

In contrast, while poor weather, malfunctioning rollers, and thickness of asphalt mix may all influence operational efficiency or effectiveness, they do not directly relate to the risk of structural damage. Therefore, they may not warrant an automatic prohibition of vibratory roller usage in the same urgent manner as the risk of damage to underlying structures.