1. Assistant Professor, Dept. of Civil and Mechanical Engineering, United States Military Academy, Bldg. 752, Mahan Hall, Room 329, West Point, NY 10996 (corresponding author).
2. Research Assistant, Univ. of Texas at Austin, 10100 Burnet Rd., Bldg. 177, Austin, TX 78758.
3. Associate Professor, Univ. of Texas at Austin, 10100 Burnet Rd., Bldg. 177, Austin, TX 78758.
4. Dewitt C. Greer Centennial Professor in Transportation Engineering, Univ. of Texas at Austin, 10100 Burnet Rd., Bldg. 177, Austin, TX 78758.
5. Professor, Univ. of Texas at Austin, 10100 Burnet Rd., Bldg. 177, Austin, TX 78758.