1. Professor, Dept. of Transportation and Communication Management Science, National Cheng Kung Univ., No.1, Ta-Hsueh Road, Tainan 701, Taiwan (corresponding author).
2. Assistant Professor, Dept. of Transportation Technology and Logistics Management, Chung Hua Univ., No. 707, Sec. 2, WuFu Rd., Hsinchu 300, Taiwan; formerly, Ph.D. Candidate, Dept. of Transportation and Communication Management Science, National Cheng Kung Univ., No.1, Ta-Hsueh Road, Tainan 701, Taiwan.