For resisting rutting, which design temperature criterion should be used?

• A. Lowest available design temperature
• B. Average design temperature
• C. Highest available average 7-Day maximum pavement design temperature
• D. Mid-range design temperature

Answer: (C)

Rutting happens when the asphalt surface permanently deforms under traffic when the mix becomes soft in hot weather. To guard against that, the design temperature should represent the worst hot conditions you expect to see. Using the highest available average seven-day maximum pavement design temperature ensures the mixture and layer design are strong enough to resist deformation during extended heat, not just on a single unusually hot day. The seven-day average smooths out daily spikes but still captures a truly hot period, giving a reliable protection against rutting. Choosing the coldest, mid-range, or merely an overall average temperature wouldn’t stress the design for the heat where rutting is most likely to occur.