Final answer:
Visual inspection is the most common method of detecting unsound pavement.
Step-by-step explanation:
The most common method of detecting unsound pavement is visual inspection. This involves visually examining the pavement surface for cracks, potholes, or other signs of deterioration. Visual inspection is a cost-effective and efficient way to identify visible distress in the pavement.
Although other methods like core sampling, non-destructive testing, and laboratory analysis can provide more detailed information about the condition of the pavement, they are less commonly used due to their higher cost and complexity.