What deficiency should be allowed in straightedge measurements over a joint?

The correct answer, 3/8 inch, is significant because it reflects the industry standards for allowable surface irregularities in asphalt paving, particularly at joints. When conducting straightedge measurements over a joint, which is a critical area where two sections of pavement come together, it is vital to ensure that the surface conforms closely to specifications for smoothness. The maximum allowable deficiency of 3/8 inch represents a balance that permits some degree of unevenness while still ensuring that the pavement maintains an acceptable quality for safety and performance.

Surfaces that exceed this deficiency may lead to issues such as increased wear on vehicles, reduced ride quality, and the potential for water pooling, which can contribute to further deterioration of the pavement. Therefore, allowing a deficiency of 3/8 inch is a practical approach that acknowledges the realities of paving while still aiming for a high-quality finished product.

The other options present larger tolerances, which could result in more pronounced surface defects and compromised pavement performance, emphasizing why 3/8 inch is prioritized in highway construction standards.