1. Assistant Professor, Dept. of Civil and Environmental Engineering, Univ. of Texas at San Antonio, One UTSA Circle, San Antonio, TX 78249 (corresponding author).
2. Assistant Professor, Dept. of Railroad Facility Engineering, Korea National Univ. of Transportation, 157 Cheoldobangmulgwan-ro, Uiwang 437-763, South Korea; formerly, Assistant Research Engineer, Texas Transportation Institute, Texas A&M Univ., College Station, TX 77843.
3. Graduate Student, Dept. of Civil Engineering, North Carolina State Univ., Raleigh-Durham, NC 27607.
4. Postdoctoral Research Associate, Texas Transportation Institute, Texas A&M Univ., College Station, TX 77843.
5. Associate Professor, Dept. of Civil Engineering, Kunsan National Univ., Daehak ro 558, Kunsan, Chellabuk-Do 573-701, South Korea.