1. Dept. of Civil, Architectural, and Environmental Engineering, University of Texas at Austin, 301 East Dean Keaton, Austin, TX 78712.
2. Center for Transportation Research, University of Texas at Austin, 3925 W Braker Lane, Austin, TX 78759.
3. Dept. of Civil, Architectural, and Environmental Engineering, University of Texas at Austin, 301 East Dean Keaton, Austin, TX 78712 (corresponding author).