1. Assistant Professor, Dept. of Civil, Architectural and Environmental Engineering, The Univ. of Texas at Austin, ECJ Bldg. Suite 6.108 (MC 1761), Austin, TX 78712 (corresponding author).
2. Graduate Research Assistant, Texas Transportation Institute, Texas A&M Univ., College Station, TX 77843-3135.
3. E.B. Snead I Associate Professor, Texas Transportation Institute, Texas A&M Univ., College Station, TX 77843-3135.
4. Snead Chair Professor, Texas Transportation Institute, Texas A&M Univ., College Station, TX 77843-3135.