1. Graduate Student Researcher, Dept. of Civil and Environmental Engineering, Institute of Transportation Studies, Univ. of California–Berkeley, 109 McLaughlin Hall #1720, Berkeley, CA 94720-1720 (corresponding author).
2. Professor, Dept. of Civil and Environmental Engineering, Institute of Transportation Studies, Univ. of California–Berkeley, 109 McLaughlin Hall #1720, Berkeley, CA 94720-1720.