1. Senior Laboratory Manager, Turner-Fairbank Highway Research Center, FHWA, 6300 Georgetown Pike, Rm. F210, McLean, VA 22101; formerly, Graduate Research Assistant, Dept. of Civil and Environmental Engineering, Univ. of Maryland, 1173 Glenn Martin Hall, College Park, MD 20742.
2. Assistant Professor, Dept. of Civil and Environmental Engineering, Univ. of Maryland, 1163 Glenn Martin Hall, College Park, MD 20742 (corresponding author).