1. Assistant Professor, Dept. of Civil and Environmental Engineering, Washington State Univ., 405 Spokane St., Pullman, WA 99164-2910 (corresponding author).
2. Research Associate, Institute for Transportation Research and Education (ITRE), North Carolina State Univ., Centennial Campus, P.O. Box 8601, Raleigh, NC 27695-8601.
3. Director, Institute for Transportation Research and Education (ITRE), North Carolina State Univ., Centennial Campus, 909 Capability Dr., Suite 3600, Research Building IV, Raleigh, NC 27606-3870.