1. National Research Council Research Associate, Federal Highway Administration, Turner-Fairbank Highway Research Center, Office of Infrastructure Research and Development, 6300 Georgetown Pike, McLean, VA 22101 (corresponding author).
2. Graduate Research Assistant, Dept. of Civil and Environmental Engineering, Univ. of New Hampshire, 33 Academic Way, Kingsbury Hall W161, Durham, NH 03824.
3. Professor, Dept. of Civil and Environmental Engineering, Univ. of New Hampshire, 33 Academic Way, Kingsbury Hall W183B, Durham, NH 03824.