What is the primary tool used for straightedge calibration?

The primary tool used for straightedge calibration is the rolling straightedge. This tool is designed specifically to assess the evenness and flatness of paved surfaces, such as asphalt or concrete. The rolling straightedge allows for the precise measurement of deviation from a true straight line over a specified distance, which is crucial for ensuring that road surfaces meet required specifications for smoothness.

The rolling straightedge can be moved across the surface while directly measuring any irregularities, which helps in identifying high or low spots that require correction. Its design and functionality cater directly to the needs of asphalt paving, making it the preferred choice for this calibration task.

Other tools like a smart level or digital level are useful for various surveying and leveling tasks but do not provide the direct, practical application required specifically for straightedge calibration in asphalt paving. A manual measuring tape is typically used for measurements rather than calibration of straightedges, and it lacks the precision needed for assessing pavement smoothness. Therefore, the rolling straightedge stands out as the most suitable and effective choice for this purpose.