How is the surface tolerance of asphalt concrete paving evaluated?

The surface tolerance of asphalt concrete paving is evaluated using a four-meter straightedge because it provides a practical method for assessing the flatness and smoothness of the pavement surface over a longer span. This tool allows for the measurement of deviations from a specified reference plane, which is essential for ensuring that the surface meets the required tolerances for drainage and ride quality.

Using a four-meter straightedge is especially effective since it can reveal low spots or imperfections that may not be visible over shorter distances. It aligns well with industry standards and practices for pavement quality assurance, ensuring that the surface can perform adequately under traffic loads.

In contrast, a three-meter ruler may not effectively capture all relevant deviations, especially for larger asphalt surfaces. A digital level, while accurate, is more suited for precise elevation measurements rather than evaluating overall surface tolerance. A measuring tape, on the other hand, is not an appropriate tool for this task, as it cannot adequately assess flatness over a surface without an additional reference for straightness. Thus, using a four-meter straightedge is the correct method for evaluating the surface tolerance of asphalt concrete paving.