1. Professor, Dept. of Civil and Environmental Engineering, Univ. of Washington, Seattle, WA 98195 (corresponding author).
2. Graduate Research Assistant, Dept. of Industrial and Systems Engineering, Univ. of Washington, Seattle, WA 98195.
3. Professor, Dept. of Industrial and Systems Engineering, Univ. of Washington, Seattle, WA 98195.
4. Graduate Research Assistant, Dept. of Biostatistics, Univ. of Washington, Seattle, WA 98195.