1. Senior Scholar, Highway Research Div., Korea Institute of Construction Technology, 1190, Simindae-Ro, Ilsanseo-Gu, Goyang-Si, Gyeonggi-Do, 411-712, Korea.
2. Graduate Research Assistant, Dept. of Civil Engineering, Univ. of Nebraska–Lincoln, Lincoln, NE 68588-0531.
3. Professor, Public Policy Center, Dept. of Civil and Environmental Engineering, Univ. of Iowa, 4117 Seamans Center, Iowa City, IA 52242-1527 (corresponding author).