1. Postdoctoral Research Associate, Texas A&M Transportation Institute, Texas A&M Univ., College Station, TX 77843 (corresponding author).
2. Associate Research Engineer, Texas A&M Transportation Institute, Texas A&M Univ., College Station, TX 77843.
3. Professor and Fred J. Benson Chair, Zachry Dept. of Civil Engineering, Texas A&M Univ., College Station, TX 77843.