The design level of ESALs specified for superpave HMA mixtures is based on:

The design level of ESALs (Equivalent Single Axle Loads) specified for Superpave Hot Mix Asphalt (HMA) mixtures takes into account the anticipated traffic over a 20-year period. This approach helps ensure that the asphalt mix will be durable and able to withstand the stresses imposed by traffic loads over a significant duration.

By using a 20-year level of traffic, the design process incorporates various factors, such as expected traffic volume and vehicle types, to estimate the total number of load repetitions that the pavement structure will experience throughout its service life. This method facilitates a more robust design that accounts for growth in traffic over time, providing a sound basis for the performance and longevity of the pavement.

The other options do not align with the long-term perspective required for pavement design. For example, traffic in a 24-hour period focuses solely on immediate conditions, which does not reflect the compound effects of traffic over multiple years. Similarly, the highest anticipated temperature is not a direct factor in calculating ESALs, which are driven by load rather than environmental conditions. Finally, a percentage of the maximum theoretical density pertains more to the compaction and quality control of the asphalt mix, rather than the traffic forecast that ESALs represent.