What is an important aspect of contractor responsibility regarding check samples?

The correct answer highlights the significance of maintaining the integrity of samples in quality management systems, particularly in a roadway context. Separating layers of check samples allows for a more comprehensive evaluation of the materials being tested. This practice ensures that each layer can be examined independently, which is crucial for identifying any inconsistencies or issues within the material.

By separating the layers, contractors can more accurately assess the quality and performance of the various components, facilitating better decision-making and ensuring compliance with specifications. This practice reinforces the reliability of the testing process, providing clearer data that is essential for effective quality assurance.

In contrast, conducting tests independently can lead to discrepancies and might not reflect the overall material quality. Taking samples secretly undermines transparency and could compromise the validity of the testing process. Reporting results only when requested may lead to delays in addressing potential quality issues, which can have significant downstream effects on roadway safety and durability.