1. Virginia Tech Transportation Institute, 7054 Haycock Road, Falls Church, VA 22043.
2. Department of Civil and Environmental Engineering, Virginia Polytechnic Institute and State University, 7054 Haycock Road, Falls Church, VA 22043.
3. Department of Civil and Environmental Engineering, Virginia Tech Transportation Institute, Virginia Polytechnic Institute and State University, 3500 Transportation Research Plaza, Blacksburg, VA 24061-0536.