1. Dept. of Civil and Environmental Engineering, Public Policy Center, 209 SQ, Univ. of Iowa, Iowa City, IA 52242.
2. Ph.D. Student, Dept. of Civil and Environmental Engineering, Public Policy Center, 209 SQ, Univ. of Iowa, Iowa City, IA 52242.
3. Professor, Dept. of Civil and Environmental Engineering, Public Policy Center, 209 SQ, Univ. of Iowa, Iowa City, IA 52242 (corresponding author).
4. Ph.D. Graduate, Dept. of Civil, Construction, and Environmental Engineering, Institute of Transportation, Iowa State Univ., Ames, IA 52242.
5. Professor, Dept. of Civil, Construction, and Environmental Engineering, Institute of Transportation, Iowa State Univ., Ames, IA 52242.
6. Bituminous Engineer, Iowa Dept. of Transportation, Materials Office, 800 Lincoln Way, Ames, IA 50010-6915.